Some people somewhere are peeved about sabbaticals. "Paying Teachers Not to Teach" and such.
The short rhetorical answer: Professors are exploited. These people are so smart and so well educated and you're paying them a pittance to teach when they really should be running the world.
The longer answer takes into account the quality of life issues, peculiar features of the market incentives concerning Ph.Ds and the substantial benefits that sabbaticals confer on the academic world, and admits that on the whole professors get a fair deal that isn't in need of substantial alteration in either direction. For a portion of that long answer, check the left2right post up there including the comments, and this bit from Keith Burgess Jackson in the rare moment when I'd agree with him.