On the OP's topic of should've etcetera, I have a slightly different angle. When my daughter was in her mid-teens she had a (sort-of) boyfriend for a while who was born British but because his parents were in international jobs throughout his school years, was educated in various 'English' schools around the world. His knowledge and English was good and clear with a wide vocabulary, but for some reason, never used the spoken apostrophe to replace 'have', nor the negative not (as in don't, won't) it was always "do not","will not" - even "can" "not", and similar which resulted in a strange stilted (almost wooden) lilt to his speech. I preume this was because he rarely heard native english speech which in my experience was taught at school how to use the apostrophe correctly, including the actual pronunciation. Should've was pronounced 'should erv' etc. with the second syllable being very short. I have been under the impression that those who say 'should of' may incorrectly believe that it is lazy speech, but unfortunately they picked the wrong word to say in full (presumably because they were not taught how the apostrophe works in those words). It's a bit like those who insist in pronouncing the letter 'H' as 'haich' with an emphasised first letter, probably because they think that it is proper and sounds better than lazily dropping the 'h' sound at the beginning of a word, even wheb the word is that for the letter aitch.
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) and Language Development over Time was a wonderful part of the course. Referring to the original discussion of “could of” and “could have,” people writing the former is primarily due to the written forms of the English language evolving closer to the spoken.
