If you don't need one, I say don't get one. I like my smartphone because of what it does to get me out of tight binds. I make money transfers, and I use public transit a lot so I have a map for that. Other than that I never, ever look at it, and I think if it doesn't create a net positive for your life, you should avoid it.
I'm just concerned that at some point in the future it may only be possible to purchase a smart phone and contract. In that case I wouldn't relish just switching over to a landline number, but it is an option.
Yeah, that's pretty much where things are headed. I think it's still possible to use a smartphone conservatively, what worries me more are the contract prices and data plans. As we move to a future where we operate with smartphones only, I'm sure the big companies will find a way to exploit that.