why do know it alls feel the need to prove everyone wrong or just share it all?

ok i could never understand this. i would consider my self a know it all but i am lazy i don't like to correct people or feel the need to make my self seem like the smartest person in the room. simply because once people consider you to be smart they tend to ask you about this or that and i hate it. I've come across some college students who feel like they are so smart they have to share it with everyone. they like to correct or prove people wrong and argue to prove their points. it bothers me when they make them selfs out to look like the smartest person in the room when i know they are talking out of their ***. i could argue with them and more likely make them feel stupid but i would gain nothing from it. too much effort to argue with someone who has that know it all mentality.