A few years ago the best choice for this question would have been seeing how far their skills can take them. Today this has changed greatly, most crimes committed are financially motivated.

Profit is the most widespread motive behind all cybercrimes and, indeed, most crimes- everyone wants to make money. Hacking for money or for free services includes a smorgasbord of crimes such as embezzlement, corporate espionage and being a “hacker for hire”. Scams are easier to undertake but the likelihood of success is much lower. Money-seekers come from any lifestyle but those with persuasive skills make better con artists in the same way as those who are exceptionally tech-savvy make better “hacks for hire”.

"White hats" are the security specialists (as opposed to Black Hats) interested in helping the community in securing their networks. They will test systems and network with the owner authorization.

A Black Hat is someone who uses his skills for offensive purpose. They do not seek authorization before they attempt to comprise the security mechanisms in place.

"Grey Hats" are people who sometimes work as a White hat and other times they will work as a "Black Hat", they have not made up their mind yet as to which side they prefer to be.

The following are incorrect answers:

All the other choices could be possible reasons but the best one today is really for financial gains.

References used for this question:

http://library.thinkquest.org/04oct/00460/crimeMotives.html

and

http://www.informit.com/articles/article.aspx?p=1160835

and

http://www.aic.gov.au/documents/1/B/A/%7B1BA0F612-613A-494D-B6C5-06938FE8BB53%7Dhtcb006.pdf