I'm not going to pretend to be an expert, but, my thoughts on this are that this is just another (poorly made) attempt by Apple to keep what they perceive to be inadequate applications off of their App Store. Any side effects[1] of their decision are simply added bonuses, not part of the primary reason behind it.

[1] With the most obvious side effects being not allowing a "code once, use anywhere" environment to gain popularity and being a direct shot at Adobe (CS5's release is only a few days away).