It's important to ensure that characters have motivations that are logical and consistent within the game world - rather than just doing things because they will gain experience or whatever. Even riches may not be the deciding motivating factor in a character's choices (as far fetched as that may sound).

After all, there's also power. And glory. And arcane knowledge that brings power. And glory. And riches.

Ah, okay.

Transcript

Adam: Okay, I go melt down the robots.
GM: You don't see them in the garage.
Adam: Don't tell me they escaped?
C-3PO: {popping up} Half right.
Adam: Pete escaped?
C-3PO: He's a devious one.
Adam: Okay, he can't have gone far. I'll melt you down first.
C-3PO: What?! Why do you want to do that?
Adam: It's my quest.
C-3PO: No silly. Your quest is what you choose it to be.
Adam: Huh?
C-3PO: You can succeed at anything you want, not just what your parents tell you to do.
C-3PO: You need your own motivation. Why are you melting me down?
Adam: You called me a dorkhead.
C-3PO: That was out of character, you numbskull!