what is the reasons for fighting dose ponyboy discovers when he surveys the gang

Ponyboy realizes that each member of the gang fights for a different reason: Soda for fun, Steve for hatred, Darry for pride, and Two-Bit for conformity... but Ponyboy doesn't know why he himself fights. Darry reminds Ponyboy and Soda to run away if the police show up, so they don't get put in a boys' home.