I cant shot without mine now. Is it essential. Well you have to make your mind up really. I would say anything that helps grip things like a tree or the post and allows you some grip against your hand must be better than a bare hand.
I use one with the fingers out as I have small hands but why not try one and see.. it needs to be quite tight on the hand, more so than a normal glove as it holds your hand in a slightly curved position.