Why YSK?
The first person who typed “should of” probably heard of it in real life that was meant to be “should’ve”, they typed “should of” online and readers thought that it’s grammatically correct to say “should of” which is in fact wrong and it became widespread throughout the years on Reddit.
I hope something could start to change.
A bit like how putting “would” in a third conditional if-clause has become standard in US English (“We wouldn’t have been late if we would have taken a taxi”).
I know language evolves but it doesn’t stop my left eye from twitching whenever I hear it.