In Chinese grocery stores and restaurants, I see about as much veggie fish/shrimp as veggie beef/chicken, and it tastes about as good. But the veggie fish and shrimp take less like real fish/shrimp than veggie beef/chicken taste like real beef/chicken. So it may be that similar effort went into each, and many cultures were less satisfied with the results for fish.
In Chinese grocery stores and restaurants, I see about as much veggie fish/shrimp as veggie beef/chicken, and it tastes about as good. But the veggie fish and shrimp take less like real fish/shrimp than veggie beef/chicken taste like real beef/chicken. So it may be that similar effort went into each, and many cultures were less satisfied with the results for fish.
It may be possible to do better vegetarian “fish” with modern technology, but I haven’t heard of anyone working on it.