Ive used different clothing..Some years ago i performed in modified policeuniform, sometimes the usual balaclava, hood over face, blood etc.. Not to sound too pretensious, but it is about transformation from the usual face, when giving a performance, into something else. It can be of ritual nature, or an outfit more fitting to the subject matter treated during the concert. I have a background from metal, so this maybe comes with the territory. It is amazing to see that people you know as calm from daily normal life can be transformed into raging creatures on stage, and im sure it helps to be drenched in blood to get "into it". For it is about that really, it helps to get totally into the atmosphere of what i am doing by putting on something specific. It could easily be something i wouldnt have trouble with wearing in normal life, but when this specific piece of clothing is meant to be used as stage attire, it suddenly helps to get there. Sometimes a hooded sweatshirt is all that is needed, sometimes gallons of blood, backdrops, video etc. All about what is going to happen, what the aim of the performance is.
I guess for some the aim is to make live music while having a good time as usual daily life also, that is of course allright.