Technically, you're not supposed to fight and will get penalized at professional levels (or thrown out of the game and suspended at amateur levels), but that doesn't mean people are going to stop. It's too valuable as a tool to police the game when refs are doing a bad job, or fire up your teammates when not doing well. Fighting has reduced a LOT, like, it does not happen anywhere close to as much as it used to, but it's probably never going to go away completely.