I believe some of the reasons are due to lack of the possibillity to do a "clean install". When you have a windows 8 licence key, you can't get a Windows 8.1 ISO to install from. If you get your hand on an ISO (torrent or whatever), then you can't install it with your windows 8 key. Finding an (unlegal??) installkey, install windows 8.1, change to your legal windows 8 key, and THEN you can activate your windows 8.1.
This stupid solution brings some poor installations to surface. First install a windows 8, then opdate a lot, then upgrade til windows 8.1, then update some more, and then change key. No wounder normal people don't like to start such a job.
When Windows 8.1 CAN be activated with a windows 8 key, why the .uc. can't we be allowed to install windows 8.1 in the best possible way, without having to use an "install key", that we're not even sure is legal to use?
I have had a big search going on for finding an .ISO in my language (danish) with Windows 8.1 Pro x64. I can't download it from Microsoft as I only have an Windows 8 Pro key. But at last I have succes in finding such an .ISO, and after a clean install with Windows 8.1 I can now see some of the better things MS has been done with the OS (for my use).
All the way back to Windows 95 it was never a good idea to "upgrade" an OS, you get the smallest and the fastest system by a clean install, so WHY does MS want most of os to go through this "upgrade hell"??