It's something more fundamental. When writing software for mobile devices, you really need to optimize for power consumption. There was a recent talk at Google IO about the new polling vs pushing for web services, and it's alarming. If your Android app polls a web service every 5 minutes, it'll use something like 10% of the battery in one day (just that one app!).

Flash apps are simply not designed for optimal power consumption. Flash is designed for multimedia apps, which are generally power hogs.

I develop Flash professionally, and I'd never run it on my phone.