Some common reasons why teens hack is probably to pull a "prank" or a "joke" on people  they hate or on people they think might be to nice to punish them.  For example, I was watching MTV one day after school, and there was a show on called 'High School Stories; Pranks, Jokes and Controversies', anyway , there was a story on a kid that hacked onto the school's computer and changed all the grades on the online grade book to A's. He got expelled and spent 2 days a juvenile. I think hacking will never be something ethical because "hacking" is just another word for stealing or breaking-in onto other people's property or belongings, only in this case, this "stealing" is computerized and any laptop can hack onto another computers' motherboards.