Not a therapist myself but mine is smells. Nowhere I have been for facials or massage have given me an option on what candle or air freshener scent I would like and a few places have used vanilla, vanilla reminds me of wood lice in ice cream and make me feel ill.
As for the hair industry, I can't stand having stations too close to windows. Who wants to be gawped at when sitting there with a head full of foils? I'm not bothered by it personally but some may find it embarrassing, a bit like a therapist doing intimate waxing with the clients toes pointing an open window. Xoxo