Yes I think It depends on you if you can afford to replace the glass if you drop it then a case is not as important but if like a lot of us you can't afford to frow away 200 pound I'd use a case plus protects the phone from getting marked and scratched up while in ur pocket or bag #
I could easily afford to replace my iPhone. That doesn't mean I'm stupid enough to leave it naked and have to waste $200 replacing it. I have an Otterbox on it. That may be too extreme for some, but having a case with some sort of drop protection is absolutely necessary for owning an iPhone.