There are good technical reasons why Microsoft chose this path. However, for average XP users and many businesses, such a difficult upgrade makes Windows 7 a non-starter. Users that are more proficient will make the upgrade at their own peril, just make sure you have application install disks handy.
Yes, you can upgrade from XP to Windows 7, but is it really worth it?
No!
Just buy an inexpensive new Win7 machine instead. Hardware has improved a great deal since many of our XP machines were purchased. Money for a Windows 7 upgrade is better spent on a new computer that comes with it preinstalled. In terms of time, trouble, and a happy user experience, this is the best way to get Windows 7.
Just for reference, my old “Blue and White” G3 can run any version of the Mac OS from 8.5.1 to 10.4.11.