Windows 7 works on notebooks and also they are working in lower end machines (mostly on memory specs) where 64 bit brings no advantage, or if is any, please point it out.
Windows 8 to be 64 bit only? Why? It uses basically the same specs as Windows 7 or Vista. 32 bit brings in itself some advantages, including that if you target a software package for a 32 bit Windows, you know that it will work with XP. And if you think that most XP users are owners of 32 bit machines, and some of Win7 users are on 32 bit machine too, I see no reason why Microsoft would not want to not support such of a wide user base.
At the end I'm thinking that Linux should follow the same path, and not only for tablets: running on more platforms means that they can enjoy the beauty of Linux. Remember Ubuntu PowerPC? Many Mac users were exposed to it: if you don't want to upgrade your Mac every time with 130 dollars (as it was at the time), you will get a newer Unix like experience for just writing it on a CD.
At the end, Linux is used a lot in schools, I know they use it in Spain. Why not allow users to upgrade their beloved OS with the newest Ubuntu, Suse or Fedora?