I agree that grammar presents a minor group rationality problem. I disagree about what the problem is.
The distinction between its and it's does nothing to improve writing, either in terms of clarity or in terms of expressiveness. Reserving "their" for the plural possessive complicates writing and adds nothing. A broad class of grammatical rules fall into one of these classes. Wasting education time on these rules (I would estimate that I've spent at least 10 hours on clearly useless grammar in school) and using them as a status indicator seems like destructive behavior that should be corrected.
People who make the error may have simply spent less time in their lives thinking about the distinction, which as far as I can is probably better for everybody. If you don't understand how the error can even happen, as opposed to why people don't learn to correct it, then I think the issue is the variety of human brains (or else a failure of introspection). Personally, I get information from my thoughts to my hands by reciting; the natural failure mode is to switch between homophones freely. The difference between its and it's is an even easier substitution than most (although I believe I generally write the correct one).
Sure.
Similar things are potentially true of all aspects of grammar/spelling/word choice that aren't strictly necessary in order to convey the meaning of a phrase... for example, you'll generally no what I mean from context even if I confuse "no" and "know."
For my own part, I have a fondness for using different signals to invoke different referents (and for not using different signals to invoke the same referent), but I acknowledge that other people's mileage varies, and that we could accept a lot of linguistic/orthographic abberations without significantly reducing comprehensibility.
There's been a recent heavily upvoted and profusely commented post about things people want to learn. It's close to having so many comments in a single day that it should probably have a part 2.
However, the subject seems to inspire thoughts about what *other* people ought to know, and while that's got a good bit of overlap, it's emotionally rather different.
So, what do you think other people ought to know? Any theories about why they haven't learned it already? Any experience with getting someone else to learn something when it started out as your project rather than theirs, especially if the other person was an adult?