I was thinking (yeah, dangerous, I know) when I was a kid we didn't start wearing long trousers until about age 12, it was all bare knees and long socks, now the little wimps are wearing longs at age 5 if not earlier.
On the other hand a lot more adult men wear shorts, or those grotesque three quarter length things; our postmen seem to wear shorts in all weathers, in some ways I can see a point there, no fun walking the streets with a bag full of mail in soggy wet long trousers, however I would have thought modern technology could come up with an effective waterproof material.