I'm not so convinced that a centralized distribution authority that introduces a significant turn-around time (months or even years), patches the software as they see fit, and enforces their own licensing ethos is the best model for programmers to get their software to end-users/consumers.
Of course, there are two good reasons 'fatelf' has not been implemented before, and it has nothing to do with packages:
2) User clicks download link, drags to any directory they want.
Trying to build packages that continue to work across releases and as libraries get updated and packages change -- and operate in a compatible manner with the built-in packages -- is surprisingly difficult.
Why don't more people do it? The only 3rd-party packages I come across are RedHat RPMs, and half the time, they're broken. I almost never come across 3rd party apt/yum repositories run by corporations, and the few times I have, they've been very broken (remember Ximian? http://en.wikipedia.org/wiki/Ximian)
Of course, there are two good reasons 'fatelf' has not been implemented before, and it has nothing to do with packages:
http://www.google.com/patents/about?id=b3wiAAAAEBAJ&dq=5...
http://www.google.com/patents/about?id=MQQnAAAAEBAJ&dq=5...