There is a big difference though. People who run IE6 would be usually capable of running some more recent browser, but for various reasons choose not to. People who are stuck with Android 2.x are stuck because their hardware can't support newer versions of Android (well there are various custom ROMs that "work" with various degree of success on older devices, but not really in a usable form).

People running IE6 are doing it because their IT department won't let them upgrade.

People running Android 2.3 are doing it because their carrier won't let them upgrade.

There are certain circumstances where you want to support ie6, though not many outside enterprisey things.

ie6 has lost widespread support. Heck, google stopped supporting it three years ago