Short story: we simply haven’t gotten around to implementing it yet on Android.
Long story: when we started more than two years ago, iOS was way ahead of Android in terms of beacons and BLE adoption, so our initial focus was on iOS first. Since then, Android started catching up rapidly: Android 5.0 gained completely new, rock-solid BLE API, the adoption of Android 5.0 has grown, more and more Android devices come equipped with modern BLE chips (not the early version, terrible chips used e.g. in Nexus 4 or 7), Google announced Eddystone, etc. With all of that happening, we also started catching up our Android stack to achieve feature parity with iOS—but as you can imagine, it’s not something that happens over night. We’re mostly there now, with only a few things remaining (stickers settings, analytics, trigger engine, that’s it I believe!), so it shouldn’t be long. And going forward, our goal is full feature parity. For example, the Location Beacons we’ve just announced will come with the full iOS and Android support the day we ship out the first dev kit, next month.