Using that subtitle as the title would make it work worse for me because:
that title would be too long. many of the interfaces that show me titles would simply cut it off and I would not see the back half of it
that sentence is semantically dense and grammatically complicated. I have to put in some work to break it down into noun phrases and such and figure out how it fits together. requiring cognitive work of potential readers before they’ve even decided if they want to read your thing is extremely anti-memetic
the tone of it sounds like a dry academic paper. those are typically not very fun to read. it signals that this will also not be fun to read
Whereas the actual title has none of those problems. It’s short, it’s easy to parse, it’s conversational with a clear and compelling valence. It’s true it does not already explain why the author is worried about Chicago, but I think that’s fine—when the explanation is complex enough you should need click on the article to find it out. Clickbait is when the answer could easily fit into the title and the author chose not to do that. Here I don’t think it can.
What? I am telling you it is. Not in the sense that I can’t parse it, but in the sense that I notice the cognitive effort involved, and preferentially read things that take less cognitive effort (all else equal, of course). If I’m skimming a bunch of titles and trying to pick which thing to read, the difference between titles that lodge their meaning into my brain as soon as my eyes fall on them vs. titles that take an extra couple seconds to parse is going to matter. (Similarly, I prefer Cooking For Engineers recipe layouts to recipe blogs that require me to extract the instructions from longer-form text—not that I can’t do that, but I don’t prefer to.)
Maybe this means you don’t want me to read your post! But I don’t think that’s right. Titles are usually the most optimized-for-memeticness part of a post; I typically assume that the rest of it will be denser, and that’s fine—if I’m reading your post I am probably sold on being interested in what you’re saying. (Still better all things equal to make stuff easier to parse, when that doesn’t trade off against other desiderata.)