It's rude to lie about which school you attended.
Bob wants to come up with something interesting to say to people at parties.
Bob wants to impress people.
Bob decides to instead talk about the chess tournament he won as a kid.
Bob starts telling people that he went to Harvard.
He remembers beating the top players in his city, most of which were adults, people are impressed with Bob.
Bob is caught not telling the truth when someone who actually went starts asking follow up questions.