I think it's more that it's a game of whack-a-mole. There are an infinite number of possible scenarios you could warn about, and each one carries a small cost t

I think it's more that it's a game of whack-a-mole. There are an infinite number of possible scenarios you could warn about, and each one carries a small cost to implement, a small cost to maintain, and a risk of false-positives. Which ones are worth implementing can be hard to know ahead of time (implementing ones that have actually caused problems would be one strategy for narrowing it down, but the point remains that it's not as simple as "just check for all the unreasonable states")