Windows 7's success throws people off. I would guess that XP's age (and Vista's perceived flaws) lead to an unusually large number of tech-savvy people quickly

Windows 7's success throws people off. I would guess that XP's age (and Vista's perceived flaws) lead to an unusually large number of tech-savvy people quickly upgrading to 7. The same people would encourage others to upgrade as well, if only for the security benefits. Windows 8 does not give the technically inclined as much reason to upgrade. And as you say, Windows 8 has actual competition, among them the much simpler to use iPad.