"Why ship DEX proprietary bytecode to be compiled by the same compiler in the same way on hundreds of millions of devices to produce the same output? " Because

"Why ship DEX proprietary bytecode to be compiled by the same compiler in the same way on hundreds of millions of devices to produce the same output? " Because it isn't, or maybe it won't be? Think very hard about this. You use your device in different ways than the next guy. If someone did profile collection on the device, and then fed that back into the compiler, you'd get a different executable than the other guy. Also, building and shipping N hundred binaries from the play store seems like a recipe for disaster. In fact, i'd strongly argue doing it any other way is plain bonkers.