what?
i used to wear one on my right arm...because i sweat a lot and it would stop sweat from getting to my fingers.
it has nothing to do with technique, it has to do with hot stage lighting and, with that band... putting on an "energetic" stage show.
i thought i looked like a tool with it, but i had to... later on i moved it a little further up my forearm so it was where i rested my arm on my bass so it wouldn't affect the wood (was a warwick..didn't want to stain it)...it still stopped the sweat from getting to my hands as well.
Sweating from playing is a sign of excagurated movement, usually linking to bad technique. (Or it may just be that it's hotter over there
Unless you stand perfectly still and/or it's well below zero, I think anyone with good technique will still sweat.