Their goals are unknown, so it's not anyone's place to assume. However, the traditional hacker motive has been to discover how a (often closed) system works, figure out if there are any defects, and share the information gained with other hackers and the public. Hackers of all walks (including and perhaps especially open source developers) have a natural distaste for technology whose details are intentionally hidden from them.
You watch too many movies. Finding an exploit in something is exciting, and equally exciting is reporting your findings to others and making a name for yourself.
Also, your bit about how hackers have a "distaste for hidden details" is BS: why the heck would they care? Are they righteous do-gooders in the unending quest for truth? Closed, proprietary, systems are usually secretive because they know they've got something to hide. That's the only reason hackers focus so much on them--not because they have a moral imperative to seek the truth, but because they know that's where the juiciest exploits are.
Hackers end up being great for society in that they hack for fun recognition and not for a more evil purpose. Through their own self-interest they end up being a positive force. I would much rather have someone like Kevin Mitnick hack the pentagon before China does. That's not to say I respect why he does it.