With SteamOS coming, Microsoft needs to up its game in the handheld gaming market
(www.xda-developers.com)
It was notoriously buggy and didn't offer any reason to upgrade. Everyone stayed on 95, 98, 98se or migrated to Windows 2000. XP offered a compelling reason to upgrade with improved directx support and the rebase onto 2000 tech.
I beta tested 98, 98SE, ME, 2000, XP and a few other things.