Okay, I think I can shed a little light on this issue, being a graphic designer and knowing enough people doing similar work.
First of all, I've switched. I switched WAY back on the day it came out. My problems have been few, but I am admittedly a lot more tech saavy and adventurous than your average mac creative.
5 reasons why folks I know haven't switched from os 9:
1) Many are still using 8.6 or 9.xx. They are suspicious, almost superstitious folks who believe if they're computer is running well, and their software is up-to-date enough to get through the printer's, then there's really no reason to learn how to drive again. They're comfortable, busy and don't have the time to learn something new, even if it is remarkably better. These are folks who learned their trade using wax machines, knives and paste-up boards - they know little about their macs and like it that way, as long as it works.
2) Costs. Upgrading to OSX does mean for most people, buying a new machine, a requirement that Apple obviously had in mind. Though most would love new machines, they often don't have the power to do this themselves, and need to either convince a purchaser or justify for themselves spending 10-12 grand on new hardware and software. My experience with older designers, like late 30's and up, is that they use their macs until they are obsolete. Then they go all the way with new gear to last them another 5-7 years.
3) Quark is the publishing industry standard, as much as it drives me nuts. Though it works fine in classic mode (though much slower), the fact that it is not yet carbonized and that some major publishing industry leaders have expressed concerns about OS X, are both reasons why people will hesitate. No one i know actually LIKES using os 9 in classic mode, and until they can go ALL OSX, they'd rather not bother.
4) The folks I know doing video and TV / documentary work are a particularly suspicious crowd, probably stemming from the voodoo needed to make legacy AVID systems work right. Though most of the people i know are now using Final Cut in some capacity (and loving it), again, they're familiar with os 9, are busy, and won't switch till they have to. That and many of they're little plug'ins and one-timers aren't available on os x, or will take a significant amount of time to regather and get they're systems configured the same way as in os x. That time and bother alone is a reason to stay with what works.
5)Finally, and I think this is a biggy, many artists and creative folks doing higher to high end work really are waiting for the holy grail. We're well aware of the discrepancy in speed between macs and pcs and have been waiting and will likely wait until Apple releases some next-generation, kick-ass, compelling hardware. ipods and itunes alone won't do it.
And to wrap up, I suspect that Apple already knows it has the creative market pretty well tied up. It is focussing on exciting those customers about the future and putting it's real energy into the consumer market where it stands to make the largest short-term gains. The creative fields will fall in line over the next few years as software makers (and Apple) give them more compelling reasons to upgrade.