Really? I can think of a number of things, especially for newer players like me:

1. Talking to people you don't speak with outside of the game.
2. Exploring new areas, trying out new things.
3. Just screwing around for the hell out it, taking crazy risks, etc.

The mindset about "everything must be about getting more gil, more exp, and better items" is what often frustrates me about modern MMOs.