dude you just made it 11.
maybe 10% of this thread is actually related to stage appearance. maybe half of that 10% is of substance. That's ok considering that the OP was tongue in cheek and poking fun of the situation for the most part.
Truth be told, every gig has a written or unwritten dress code. The trick is knowing what that dress code is when it hasn't been discussed. No point in anyone being defiant and all "I wear whatever I want- rocknroll furever, beaches!!!!!!" and going off the rails on an internet forum, there are no absolutes when it's not written in the contract. Some gigs shorts might be ok. others shorts might be in poor taste and make the band look like Carl Spackler just clocked out and picked up a guitar (that might be cool on Halloween, but Muffy's wedding would be a bad call for the floppy hat). We should all try not to get our knickers in a twist and think about it. Making a blanket statement that "I have to wear shorts on stage because XXX" is just as silly as "no one should wear shorts on stage ever".