why do people hack?

Some genuine reasons, such as helping companies avoid being hacked. Who better to combat hacking than a hacker?

Personal reasons. I had a family experience recently that was a little scary regarding my mum and her recently divorced husband. Certain hacking abilities would have been very handy. Especially as the police said they could do nothing.

Likely the main reason is that it's got the whole voyeurism aspect to it. I can see you, you can't see me king of thing. Like being a spy... while sitting in bed eating chips!