That's because you're not supposed to see the other ways they're fighting. If you can tell any other kind of battle is happening, the person who shows it is losing.

[ Ash sits back, done with the food despite not having eaten but half. ]

Money. You've probably seen people fighting with it, over it. If not actual money, then something else they put value on.

[ Such as bargaining over a slave. ]

A talkshow host. She makes a lot of money getting people to spill their dirt on television and sometimes gives out cars.