Disney Online's Mike Goslin (of Toontown Online and Pirates of the Caribbean Online fame) said in an interview with Worlds in Motion that it's important for MMO projects to "support as low a minimum spec PC as possible."
PC gaming is often criticized for being too expensive. You can buy an XBox 360 for $350 or a PlayStation 3 for $400, but a desktop PC equipped with the hardware necessary to smoothly run the very latest games usually costs $1,000 or more. That's a barrier to entry for many would-be PC gamers.
Supporting low-end hardware isn't just important for children's and family games. A while back SOE CEO John Smedley told WarCry that "the biggest thing that hurts [Vanguard] is the high system specs." If the MMO genre is carrying PC gaming on its back, shouldn't MMO developers do everything they can to make their games accessible to a large audience?