I was never taught it ever, anywhere! And I can't imagine it being good on the gear.
I saw it done by a pilot and thought he was just showing off... I'm surprised at how "commmon" it seems to be. I also noticed people doing it at competition in order to "hit" the first landing sections of runways to get the max. points. Because of a number of bad results (i.e. damaged gear) they then forbid it, which I think is a sensible idea.