I think you've hit upon the typical upgrade cycle of Windows. Those who've established their systems in one version will skip the next. Whilst those not upgraded to the current version or is new to Windows will go to the next.

So if you've been using 7 for sometime, you're likely to wait for 9. Most XP users skipped Vista and upgraded to 7. Those who've been using Vista will likely upgrade to 8. Those new to Windows will get 8. In fact, it's probably 8 that's attracted them to Windows. It's possible newcomers "way back" bought a PC because they wanted Windows 7.

Naturally, the only ones who buy each subsequent version are nerds. NERDS! Those guys will try anything.

Unnaturally, the only ones crying about subsequent versions don't matter because they don't like to BUY anything.