English speakers ought to know that its is the possessive adjective and it's is the contraction for 'it is'. It drives me crazy when people use it's to mean its, and I do not understand why they do it. Do people not learn how to write by reading? (I certainly did, and I don't see how else you could do it, but I realise I'm somewhat abnormal.) Or is the incorrect use of it's so ubiquitous now that even if people learn to write by reading, unless they read mostly stuff more than ten years old they aren't being exposed to a data set from which they can infer the correct rule? Or is it more a question of being published on paper than of age? And incidentally, does anyone know if schools have stopped teaching this and similar rules? (And if so, why?)
ETA: At least two people downvoted this, so perhaps I should make the following two points more explicit.
My comment was not intended to be censorious in tone (and rereading it I still don't think it is). The bulk of what I wrote takes the form of wondering about the cause of this, to me particularly irritating, phenomenon. (Thanks to Vladimir M, I am a little less confused now.)
The reason why I find the phenomenon so irritating is primarily that I value my ability to effortlessly produce correct grammar, spelling, etc., and seeing the same mistake consistently a large enough fraction of the time bollixes up my machinery, tending to decrease the effortlessness with which I can perform correctly. Also, I fear that others are subject to the same effect, and that there could be a threshold of criticality, and even that that threshold may already have been reached. So it's a (fairly minor) group rationality issue.
The error that bothers me the most is using "loose" to mean "lose".
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?