I've always been told and believed this too, and can see why it should be true - a high kick is easier to see coming, sacrifices a lot of your own balance, runs the risk of being caught and messed around with, leaves you very open to some sort of counter and so on. If you want to kick high, join a chorus line.

However, I've recently started cross training in muay thai and there, going for a kick in the ribs seems to be considered a good idea.