who knows...but i'm finding this more and more to be honest.
at last practise, the band before us didn't clear out of the room until gone the time we were meant to start, and then no apology.
i've seen bands 'soundcheck' and play half the songs in their set (nobody obviously told them that you don't need to do whole songs to soundcheck !!)
sadly, musicians are no different to the majority of the public...they're stupid, self-centred and arrogant.