why are people jerks?

Answer 1

Two reasons: (1) we are selfish, as in want to please our own wants and needs, and (2) we are different, as in we do things differently, want different things. Between the two facts of human life, it is absolutely certain that someone, sometime will seem like a jerk to you. If you haven't realized it, you will at sometime seem like a jerk to someone else. Which is probably why the answers are just lined up long and early beneath your question.