Every character needs a motivation to get them interested in the adventure that the GM lays before them. For some it might be a thirst for adventure, or a desire to travel and see the world beyond the town they grew up in. It may be a wish to do good deeds, to rescue the princesses of the world from the dragons, or to overthrow the evil despot. Some have a calling to serve the gods of their world. Others seek knowledge and arcane power. The occasional person may be seeking justice or revenge for a wrong inflicted on their family or village.

These are all good, flavourful motivations.

Then there's the character motivated by a desire to gain wealth. Which is also kind of okay. After all, many real people in our world are motivated strongly by this, so there are bound to be such people in your game world.

Now, imagine if when George Mallory was asked, "Why do you want to climb Mount Everest?" he replied, "For the experience points."

Transcript

R2-D2: TL;DR: The Senate sucks. Seriously.
C-3PO: Except for noble Senator Binks. We have to get the Peace Moon plans to him on Naboo. Join us... and together we can save the Galaxy!
Adam: Nice story. But it's not going to work.
C-3PO: What?
Adam: I'm not going to blow my first quest by letting you out of this garage.
R2-D2: That quest will give you 50 XP, tops. Saving the Galaxy will be worth... well more experience than you can imagine.
Adam: I don't know, I can imagine quite a lot.
R2-D2: Plus, we get to rescue a Princess. Look, hologram!
Leia: Look, the problems of two people and two droids don't amount to a hill of space pears in this crazy galaxy.
{beat}
R2-D2: Okay, that might not be the best sell of this mission.