No more insane than all the linux distributions which compile programs from source. It allows new architectures to be introduced without requiring that the dev

No more insane than all the linux distributions which compile programs from source. It allows new architectures to be introduced without requiring that the developer compile them into the APK - and with all the architectures Android supports, that could become large anyway. Compiling on the device allows the manufacturer of that device to ship a compiler optimized for it. It is possible though that Google could do some compilation steps on their servers, and deliver those through the play store - but the main advantage would be a decrease in installation time.