Its definitely a user preference thing. I have one on mine and love it, while others never have had one and never want one.
I think the one thing to consider...how do you use it? Just you in the living room where it stays in the house? Or do you toss it in your bag and carry it around with others possibly using it?
If you're in situations where you could damage it, then it may be a good idea. But if you're never out of the house, then you may be okay.
For me? It's a $500 investment and I want to protect it and keep it in good shape for as long as I can....so it's never anywhere 'naked', both front and back. But I also toss mine in my backpack and carry it around.