Comment 31 for bug 32389

Fiddling around with bootloader configs isn't trivial. Such files have to be parsed and constructed carefully to ensure a clean boot process. You also have to consider extensive customizations of the menu.lst which go beyond the scope of an 'update-grub' generated file. Besides, users may not be amused to see their carefully crafted bootloader configs being modfied. Another problem is, that you don't know if a user actually uses grub to start his/her system. You have to consider many cases and all of them require a fair amount of testing.
By letting the nvidia-glx package collide with usplash, you don't need to mess around with user configs. In addtion, users get aware of the problems _before_ they install the driver. You see at once that you can't have both the nvidia binary driver and usplash. This is what the apt package management is made for.
The removal of ubuntu-desktop might be scary, but it is still better than a screwing up a system (which might not be trivial to fix for a beginner). On the other hand, is the dependency of ubuntu-desktop mandatory? All that usplash does is to add some eye candy to hide some cryptical boot messages. Or does it peform some other tasks I'm not aware of?