@Indy,
The top two reasons would be:
1. Hardware refresh. The machines are already 5+ years old.
2. To stay on a supported OS. Windows 7 is entering extended support and exiting mainstream support.
I'd say the biggest reason would be hardware refresh. Otherwise, there is nothing wrong with Windows 7.
JamesNT
We have NEVER had a client ask for W8, so we are still upgrading fresh machines (or ordering) with W7Pro.
Many clients are buying new machines as part of their hardware refresh/upgrade process, but sticking with W7Pro with the obvious reasons.
Microsoft will have to either provide a valid reason for practices to upgrade, or empty W7Pro from the market; "Just Trust Me" is no longer a valid answer from ANY VENDOR as to why a practice should take an upgrade.