People commonly use one’s ability to differentiate between ‘your’ and ‘you’re’ and ‘its’ and ‘it’s’ as a judge of one’s character or value. For example it’s not uncommon to see “Must know the difference between ‘your’ and ‘you’re'” as a ‘what I’m looking for’ on a dating profile.
I don’t think knowledge of the difference between the various grammar rules is a particularly good measure of one’s intelligence, because the rules are arbitrary and seem contradictory at times.
I threw the dog’s ball.
Ok, cool. The apostrophe indicates possession.
The dog gave me its ball.
Oh no! All of a sudden the rules change! No apostrophe here! Why not? The ball belongs to ‘it’ doesn’t it?
Give me your ball.
Again, no apostrophe.
It’s easy to see how someone might think that
Give me you’re ball
Is the correct grammar here, using an apostrophe to indicate possessiveness.
Sure, correct usage of ‘your’ and ‘you’re’ probably is a pretty indicator of a particular kind of intelligence, but I don’t think people should be written off or not valued, purely based on book smarts. For example someone might not have the best spelling, but know their way inside and out of a motor engine, and still contribute that way.
I myself that I often slip the wrong spelling out, especially when live chatting.
More to the point, there are other indicators that are far more important. For example for me, a belief in horoscopes or denying the efficacy of vaccines is far more of a turn off than incorrect spelling.