You've probably read about Android market fragmentation and wondered just how big a deal it is. This visualization spells out the problem tangentially: there are almost 4,000 unique Android devices out there running a single app available on Play. And only a very few of them run the most recent version.
The image was put together by Open Signal Maps to visualize the distribution of devices using their app. It includes data from 681,900 users, and breaks them down into almost 4,000 devices. Admittedly, that number is artificially high, because custom ROMs report identities differently.
But, the point here is that developing for Android is no longer as straightforward as it once was. With so many devices and an ever-expanding catalog of operating systems to cater for, it's hardly surprising that Android support is shaky at best. By contrast, a similar image for an iOS app would only feature a handful of devices.