Why is it so many people today don't seem to know the difference between "woman" and "women"?

Woman: a single person of the female gender.
Women: a group of 2 or more people of the female gender.

Updates
3 mo
An example I just found here seconds ago.
"Would you date and have sex with a plus size women? or is this just a fetish?"
I guess nobody but me also knows nothing about proofreading?
Why is it so many people today don't seem to know the difference between "woman" and "women"?
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