This one puzzles me as well.
As a user, the focus should be on what can be achieved, and how resource-efficient it is in operation, not on the low level details of how it gets done (that's a developer concern).
So I'd ask the same thing ... what is it that you need/want to do that this approach doesn't offer?
I asked the same question in an Android discussion, and the responses were, from a consumer perspective, fairly ludicrous. Things like "run a mail server", or "run a folding client". Really? On your phone? You don't have a better way to do that?
Anyone can come up with contrived requirements that will defeat any set of capabilities. In real world terms I am at a loss to come up with any truly interesting/useful (as in enough people would care that it actually matters) use-case that these capabilities do not facilitate to the same degree that having apps constantly running full-bore (or at reduced priority) would also resolve.