Well - also WINDOWS 7 has been sold for how many years? And windows 8 for how long ? I am pretty sure that when windows 8 is the age of windows 7 it should have more market share. Many people with windows 7 just are not "upgrading" or replacing their windows 7 machines just yet.
Windows 8 is a pretty poor reason all alone to purchase a new PC (or HTPC) in my opinion. I'd much more likely do it (and have) to get better hardware or performance and not just to get WIN8. Many windows 7 owners just are not ready yet. But windows 8 was different enough that many hardcore 7 users like me are hesistant to make the jump. I think if they kept the start menu and the traditional feel of 7 even if it was just a "win 7 mode" it would have increased the adoption rate.
It really is a pretty modern and high performance OS. Many windows 7 people bash on it because it's too different or they are not ready to upgrade but I don't think it's anywhere near as bad as some people say. It seems legit to me. I just hate being the early adopter because drivers and programs and such are PITA at first launch. I jumped into win7 after a year- and I am basically ready to jump into 8 anytime now but I am just not seeing a good deal on it yet. Plus I am really comfortable with my win7 and there is nothing to be gained with win8 from what I can see. Time will change things. I remember when people were still on XP when windows 7 came out.
"Too much is almost enough. Anything in life worth doing is worth overdoing. Moderation is for cowards."