I remember convincing my sister to wrap a bicycle chain around me and lock it up tight and shove me in a closet. Despite the fact that we'd use a very sophisticated and nigh unpickable padlock, I emerged victorious a few minutes later. Little did she know I had employed the Houdini method of escapology -- I had taped a spare key to my foot. Despite my willingness to cheat, by then I was already adept at picking smaller locks -- the little brass locks kids buy, as well as diary locks and cheaper commercial padlocks. It was good, geeky fun.
Kids are always playing with locks, because locks define boundaries -- growing up is always about testing boundaries, and about setting them. You keep big brother from reading your diary, or little sister from stealing your lip gloss. For geekkids, there is an added, technological element -- a refusal to allow a puzzle with an obvious solution (a key or substitute) to defeat them. Most geek(kid)s don't want to break into a locked area to commit larceny. It's purely curiosity -- geeks dislike having artificial limits placed on them.
This mindset is demonstrated in adult geek culture. Many hackers (in the good sense of the word) are skilled lockpickers -- they study the innards of a lock the same as they would a computer's guts. There are "lockpick workshops" at most major hacker conventions where various models are tested. In 1991 MIT hackers released a definitive Lockpicking Guide which has been distributed widely by PDF. (In)famous hacker Kevin Mitnick's business card is metal with usable lockpicks that can be snapped out of it.
(By the way, if you can get to Las Vegas this weekend, there will be a "Lockpicking Village" at the Defcon hacker conference.)
Speaking of limits, most parents will want to place clear guidelines on their kids' explorations. The ability to pick locks does not mean it's okay to violate others' property rights and privacy. At same time, knowing that clever children with agile fingers and bent pieces of wire are creeping around the house forces Mom and Dad to up the ante securitywise. Is Dad's gun cabinet off limits? Better make sure the padlock is up to snuff. This is its own reward because it increases security against actual evildoers.
By the way, I wouldn't recommend buying lockpicking tools unless you're a locksmith by trade because they are illegal in some areas and suspicious in most others. On that note here is a good how-to guide for using non-professional tools to open locks.
And finally, a couple of links:
The Lockdown, a security blog with a focus on locks.
TOOOL: The Open Organization of Lockpickers