Not for the developer. For developers, compiling in advance would just slow them down and remove a lot of the cool things you can do with Java today like hot-swapping and reflection.
Not for the user. The current system is totally transparent to the user.
You’re proposing making things simpler for the Android OS, but worse for the developer. That’s the exact opposite of what they want. A lot of Android is quite complex in ways that make things easier for developers, on purpose.