Not sure if I can agree with that for 100% because I look at myself with my current devices and I often delete things just because they sucked initially, but later got better. My job requires that I'm driving or on planes literally 80% of the time so most of my downloading comes over the air and I depend on a lot of apps to get me through my personal and work day.
I'll agree that this probably affects a very small percentage of users, but it still affects people.
I don't know about you, but if I'm not using an app, I delete it. I don't need my phone cluttered with crap that I'm not using. But, just because that app sucks now doesn't mean it won't get better and I've reinstalled plenty that have made such a jump.
If this is true, though, means that it's just better to leave anything that you download on the phone despite whether or not it's currently being used in hopes that it gets better just for the sake of convenience.
And I doubt this has as much to do with DRM as it's probably a way for AT&T and Apple to help reduce network bandwidth and profit on it at the same time. Factor in how many downloaded apps there are and how many happen all the time and that's quite a bit of bandwidth. This is just a form of bandwidth control.