Minor correction -- no version of IE (or Safari if we want to be technical) on Windows XP supports SNI. IE7 on Vista supports SNI, but not on XP. Also, Android 2.x is still pretty relevant given that it currently represents 9.6% of active Android users. The original Kindle Fire did not support SNI, though I believe with the second generation it did support SNI. Anyone with a pre-BB10 Blackberry also does not have SNI support.
Trust me, I would love to go SNI-based for SSL, but support wise we're just not there yet.