A few things that seem relevant (5 things, but maybe not crystallized in the right way to be 5 separate answers to the OP’s question):
Quantity: mismatch between natural quantity produced and quantity desired. Maybe I can plant an apple tree & pick the apples, but I don’t want a whole treeful of apples. Maybe the most efficient way to make t-shirts is to build a big machine that makes a million shirts, and a process for making just 10 of them is wildly inefficient in terms of resources per shirt. (related keywords: economies of scale, capital investments)
Timing: maybe I want something now & it would take half an hour for me to make it (and what I’ll want is unpredictable, I can’t keep a giant inventory of everything I might want—though maybe the “all of us liked exactly the same objects exactly the same amount” supposition erases this issue). If I need to plant a tree and wait for it to grow apples that’ll take years. Building the giant t-shirt machine might involve more than a single lifetime of person-hours of work.
Some things you can’t do for yourself: if I Matrix-learn how to give good massages, that won’t let me get a good massage—I need someone else to do that. That requires making some kind of deal with another person (maybe I give them a massage some other time?), which is at least kind of like trade. What counts as “trade”? Some simple cases seem not that trade-like, e.g. I play tennis with someone because you can’t play a tennis match by yourself, although we could frame it as trade-like: I’m providing them with a tennis opponent and in exchange they’re providing me with a tennis opponent. The massage exchange seems more trade-like (because asynchronous?), other cases where we aren’t just exchanging the exact same service even more so.
Some production involves multiple people: Maybe it takes multiple people to carry a heavy object, or to pick apples (one in the tree & one on the ground with a basket?), or to operate a giant machine. Or people decide they’d rather do it together with other people (e.g. because the total quantity produced is more than any one person wants, or to finish the job more quickly). So there needs to be some kind of deal between the people on how to divide up what they produce. That also seems kind of like trade. Less so in some simple cases (a group of people dividing up the work equally and then dividing up the output equally), more so as it gets more complicated.
Complicated many-person coordination: Maybe a bunch of people work together to build, supply, and operate the giant t-shirt machine and divide the t-shirts between themselves. But the most efficient way to get the screws for the machine is with a giant machine that produces way more screws than the t-shirt machine needs, so most of the screws are used for other purposes. And the most efficient way to make the fertilizer for the cotton fields involves making way more fertilizer than is needed for the t-shirt cotton. Etc. So we have multiple giant teams, partially overlapping, e.g the screw-machine-makers have a small role in the t-shirt production & in the production of many other things, and so get a little share of each. With long supply chains this might look more like screw-machine-makers bartering screws for t-shirts rather than screw-machine-makers being part of the t-shirt team. And if you think about schemes for arranging all of this, those can start to look more like trade and an economy, e.g. all these people communicating & coordinating to figure out how much to make of each thing and where to send it and so on might want to use something that looks a lot like prices (related keywords: the knowledge problem).
A few things that seem relevant (5 things, but maybe not crystallized in the right way to be 5 separate answers to the OP’s question):
Quantity: mismatch between natural quantity produced and quantity desired. Maybe I can plant an apple tree & pick the apples, but I don’t want a whole treeful of apples. Maybe the most efficient way to make t-shirts is to build a big machine that makes a million shirts, and a process for making just 10 of them is wildly inefficient in terms of resources per shirt. (related keywords: economies of scale, capital investments)
Timing: maybe I want something now & it would take half an hour for me to make it (and what I’ll want is unpredictable, I can’t keep a giant inventory of everything I might want—though maybe the “all of us liked exactly the same objects exactly the same amount” supposition erases this issue). If I need to plant a tree and wait for it to grow apples that’ll take years. Building the giant t-shirt machine might involve more than a single lifetime of person-hours of work.
Some things you can’t do for yourself: if I Matrix-learn how to give good massages, that won’t let me get a good massage—I need someone else to do that. That requires making some kind of deal with another person (maybe I give them a massage some other time?), which is at least kind of like trade. What counts as “trade”? Some simple cases seem not that trade-like, e.g. I play tennis with someone because you can’t play a tennis match by yourself, although we could frame it as trade-like: I’m providing them with a tennis opponent and in exchange they’re providing me with a tennis opponent. The massage exchange seems more trade-like (because asynchronous?), other cases where we aren’t just exchanging the exact same service even more so.
Some production involves multiple people: Maybe it takes multiple people to carry a heavy object, or to pick apples (one in the tree & one on the ground with a basket?), or to operate a giant machine. Or people decide they’d rather do it together with other people (e.g. because the total quantity produced is more than any one person wants, or to finish the job more quickly). So there needs to be some kind of deal between the people on how to divide up what they produce. That also seems kind of like trade. Less so in some simple cases (a group of people dividing up the work equally and then dividing up the output equally), more so as it gets more complicated.
Complicated many-person coordination: Maybe a bunch of people work together to build, supply, and operate the giant t-shirt machine and divide the t-shirts between themselves. But the most efficient way to get the screws for the machine is with a giant machine that produces way more screws than the t-shirt machine needs, so most of the screws are used for other purposes. And the most efficient way to make the fertilizer for the cotton fields involves making way more fertilizer than is needed for the t-shirt cotton. Etc. So we have multiple giant teams, partially overlapping, e.g the screw-machine-makers have a small role in the t-shirt production & in the production of many other things, and so get a little share of each. With long supply chains this might look more like screw-machine-makers bartering screws for t-shirts rather than screw-machine-makers being part of the t-shirt team. And if you think about schemes for arranging all of this, those can start to look more like trade and an economy, e.g. all these people communicating & coordinating to figure out how much to make of each thing and where to send it and so on might want to use something that looks a lot like prices (related keywords: the knowledge problem).