When I update, I keep a version or so back just for belt-and-braces. Doing some routine housekeeping today I uninstalled version 19, as V22 isn't so far away. It also uninstalled my product key, my library paths, and for all I know my toothbrush and spare underwear.
It's an unfortunate oversight of Microsoft that they've provided no way to clean up redundant entries from the Add/Remove programs dialogue. The end result is that it becomes cluttered with obsolete entries for old versions that no longer exist (having been replaced by a newer version. This is compounded by the uninstallation data being unable to distinguish between versions, thus creating an almost perfect booby trap for users, as many have discovered to their cost.