I can say the same thing about OS X upgrades. I'm slow at upgrading my Apple software and OS. I upgrade the OS due to the low price, but even prior to upgrading, I understand that there's little benefit for me to upgrade. To me, if it works, then don't "upgrade". Besides, many of Apple's free OS and software upgrades only exist to ensure that I'm still compatible with the iTunes Store so that they can continue to sell movies, music, and books to me (which I don't purchase). They're the primary benefactors of me upgrading, not me.
This Windows 8 upgrade may be the same for Windows 7 users, but personally, I believe this is a bigger upgrade than Snow Leopard or Mountain Lion.
The only reason Windows users won't upgrade is because Mac users appear to be more willing to spend money than on their Macs than Windows users are for their computers.
Also, uptake is slower because businesses aren't going to switch to a new OS very quickly. My hospital is still on Windows XP. It would be too costly to change OSes.