[takluyver]

Agreed. Of course it's possible in theory for every developer to have their own secure, reliable auto-update mechanism. But it's not easy - the docs of The Update Framework describe some of the challenges.

If every app handles its own updates, that also means that either you've got N background auto-updaters running, or the check has to wait until you run the software - and potentially get exploited by a hole patched in the update it's just downloading.