Background: A small, dainty, first-year, female student was roaming around the campus of Harvard University and looked lost. A tall male upperclassmen approached her.Why do people mistake would of for would have?
When you say would of instead of would have, you’re substituting the preposition of for the auxiliary verb have, which is grammatically incorrect.
Upperclassman: “Excuse me miss, but you appear to be lost. May I be of assistance to you?”
Female: “Yes, you can help me. Can you please tell me where the library is at?”
Upperclassman: “Young lady, we here at Harvard University never end a sentence in a preposition!”
Female: “Allow me to rephrase my question. Would you please tell me where the library is at asshole!”