I'm not under 18, but personally refuse to use Paypal on the grounds of not wanting to support criminal activity (see Wikileaks blockade for the beast example), and really it's the same for CC. I'd probably have bought Minecraft ages ago if they'd support payment through other means, for example, PaySafeCard.

But anyways, I generally think it's pretty nonsensical to imply that piracy is a question of a maturity. Young people might simply have other reasons to pirate.