"OP's suggesting that people who use could of, should of, would of can not seem to realise what they are doing, substituting 'of' for 'have'.
Yet at the same time, they don't apply that "rule" for substitution in all their language, because if they did, they'd say 'Of you brushed your teeth?'"
When I'm angry/stressed, I go very Scouse. I certainly don't write how I speak, as don't many people with regional accents, that they are proud of.
I would never, in my reports for Court, write, "X's Grandmother is proper sound". Or that "the house was hanging. Then I went into the Kitchen and that was minging". But, for quickness in conversation with some people, I would use that description and they would know exactly what was meant by that.
So why should anyone have to speak how they write?