Why advance your science when you have lots of magic to go around. Especially if that includes enough to launch castles in to orbit among the stars. I'm always intrigued by magic as science worlds. Because they lay down different rules about this possibly unlimited energy source that powers entire economies and countries. It's one of the reasons I find D&D's Eberron so inviting. This contrasts starkly with settings like greyhawk where the implications of the higher level magic users doesn't trickle down to the lowest levels so there's a disconnect between where you start out and soon after you gain a few levels. I have to admit I've not been much a fan of the "medieval europe but there's some magic dudes running around that have no effect on anything other than creating random monsters and dungeons for the party to fight" settings. Still haven't read planescape or spelljammer though I've heard those are good. Some of the most amusing thought exercises I've read involved figuring out how all these magical people running around would change things from the medieval cesspool where most settings begin.