Why do people hack?

Because that's where the money is:

Hackers have struck one of the world's largest internet dating websites, leaking the highly sensitive sexual information of almost four million users onto the web.

The stolen data reveals the sexual preferences of users, whether they're gay or straight, and even indicates which ones might be seeking extramarital affairs. In addition, the hackers have revealed email addresses, usernames, dates of birth, postal codes and unique internet addresses of users' computers.

...

Within hours of the data being leaked, hackers on the forum said they intended to hit victims with spam emails, and Mr Harper has been targeted with virused emails since his information was made public.

Online crime experts believe the after the initial spam email campaign, hackers will now begin trawling through the data for potential blackmail targets.

Blackmail seems to be the big win here, although there's obviously more risk than your usual hacking situation.  But organized crime has been a big player in the black hat community for ten years or more, so this is just a new source of data that they'll use the same way.

And I love this part:

Shaun Harper is one of those whose details have been published. "The site seemed OK, but when I got into it I realised it wasn't really for me, I was looking for something longer term. But by that time I'd already given my information. You couldn't get into the site without handing over information.

"I deleted my account, so I thought the information had gone. These sites are meant to be secure."

You keep using that word.  I do not believe that it means what you think it means ...