There are several reasons I can hypothesize as to why you no longer see Shorts that are shorter than culottes are:
• Shorts that shorts are for little children, mature people have grown out of them.
• They are fine if you are a foreigner, if in a British school, Japanese school, or some Asian port city, then it is OK.
• That was old-style, sagging your pants half way off your arse is much cooler; you will see rappers with and without talent < ahem Justin Bieber, ahem > wearing them saggy.
• There are too many closet pedophiles on the streets, they see a boy in short shorts they will kidnap them right off the street in front of McDonalds.
• The biggest reason (or the reason people will deny or get pissed off the most) it appears too gay, to wear them that short you have to have ”some sugar in your tank”.
Boys and even men can wear short shorts…….just not in the US. ~~