Search for knowledge:
- learning to hack something, because someday it might be very helpful
- to understand how it's possible to hack into something, so when you create a site (or something you hacked before) you know the ways that someone could penetrate, and you can protect yourself from it
- hack into a site that hides information that you need, or would like to know about
etc.
That's a list why I would hack, if I knew how