People are stupid. And annoying.
Some people are not always the wisest...and some can be a pain in the arse at times, but I don't think I'd be so bold as to throw a blanket over everyone and call them annoydiots.
I do agree with you, though, there were many who were afraid to let go of their security blankets and try something new with XP. In fact, I know someone who
still refuses to let go of 98 and will actually reformat a brand-new XP machine to install 98 on it. Thank goodness progress does not hinge upon people like him, otherwise we'd still be trying to get the wheel adopted/put to good use.
Thankfully, there are some more adventurous folk around who are willing to move with the times, embrace progress, and it's these who Microsoft, Apple and IBM, etc, target with their newer technologies. Eventually, word of mouth spreads from satisfied customers and others figure 'oh what the heck' and give it a go.
It's likely that MS considered the initial reluctance to upgrade to XP when Vista was released, and, while preparing Vista's first service pack, is riding out the initial slow period because it wasn't until SP1/SP2 for XP were released that sales picked up.
Having tested Vista through the various public beta stages, I was quite happy to buy the Ultimate version when released in January 07, and I can honestly say that I have no complaints about stability or reliability, drivers or compatibility, all but my sound card worked immediately, and even that has now been resolved so I'm very happy with Vista. In fact, at least a dozen people I know have upgraded to Vista based on my happy experience with it, and to date all are happy campers with their decision.