I would argue that the target audience of the app store isn't tech-savvy enough to do this anyway. Sure, it's easy to HN readers, but to the general public it probably "sounds too hard."
That's what people said about piracy on the iPhone, but I know plenty of non-tech savvy people who use Cydia or whatever to get free apps.
I think the real reason for the popularity of cydia is that 1) it has a user friendly UI 2) you can get apps on it that will not make it to the app store and 3) some people are just too cheap to pay for some apps and use it to pirate them