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.
“Should’ve” and “should of” are pronounced the same, what are you talking about? There’s no way you can mix them up in speech. Are you even a native English speaker?