Is there an explanation as to how the survivors get their haircuts?
I'm assuming no.
Maybe the entity can transform the survivors' hairstyles at their will. It obviously has the power to deform killers and give them superpowers, so why would it not be able to cut or transform hair?
I'd like to see a barber survivor being added through DLC though, that'd be a cool character to play as. He/She would really keep a huge responsibility in keeping the morale of the survivors up. One would like to look good and survive.
Ideally, the barber would be a male since we haven't seen any pretty males in the entity's realm yet. They're either slick (Ace), slender (Dwight) or burly (Jeff), never cute. I digress.