Developers spend months of back and forth with app store employees making them happy before an app is approved and made available. Apple knew how these apps worked, approved them, then later (a month later in Wifi-Where's case) pulled them all. That's moving the goalposts of what is allowed and enforced, and adds risk to any Apple app store time/money investment. Imagine if Jobs was talking about "apps" instead of "music" in his open letter on DRM:
"Imagine a world where every online store sells DRM-free music encoded in open licensable formats. In such a world, any player can play music purchased from any store, and any store can sell music which is playable on all players. This is clearly the best alternative for consumers, and Apple would embrace it in a heartbeat. "