I see this as neither good nor bad but I don't see why owners of Intel Macs *wouldn't* want to upgrade to 10.5...
Well there are a lot of reasons. Some of them would exclude them from using boot-camp.
1. Their System is to old and Leopard will run to slow. (but will not effect boot camp because they have PPC Macs)
2. None of the features entice them to switch. Why pay Over a Hundred Bucks for an OS, the hassle of putting on a New OS. While you have a good one. $30 for boot camp is less then $130 for Leopard.
3. People who use their Macs Primarily in Windows, yes there are people who are out there who prefer Windows over OS X. In that case what point is it for them to upgrade an OS they don't use much.
4. Macs that are used for appliance jobs. (Still they would not normally need boot camp)
5. 3rd Party software that will be needed to be fully tested on Leopard, to make sure everything works so the may upgrade every 4 years.