I don't think it is switch-hitting that is so attractive, it is left-handed hitting. A great left-handed hitter is more valued than a right-handed hitter who is maybe a little better -- at least in my experience. If switch-hitting is what brings this about, then that is a good thing.
Also, from an individual standpoint, a switch-hitter (a good one) is not subject to platooning, and the worst thing in baseball almost is the be the right-handed half of a platoon.