major kernel version
1,2: 1.0 and 2.0
3: 3.0, WfW3.11, NT 3.51
4: 95, 98, NT4
5: 2000, XP
6: Vista
7: Windows 7 (but really 6.1)![]()
So the answer is, "marketing"
That's not the reason if I remember. They started count at 3 as 1 & 2 were "not real Windows". It was 3, 95, 98, ME, XP, Vista, 7; or something like that. It is kernel 6.1 because they didn't want the incompatibility problems of jumping a large kernel version (ie XP 5.1 to Vista 6.0). But yes, it mostly is marketing.