Yes, it might be handy to have a smartphone, but I've lived a full life thus far without one, and I think I'm going to keep on keeping on in my way for quite a while.
1. Too expensive. First you pay for the device, and then in order to use the device to its fullest potential, you need the huge data plan. I currently pay ~$50/month for my non-smart phone, and even that makes me grumble sometimes, especially when I consider that I use it mostly as a clock. I've asked around, and no one that I know pays less than $100/month for their smart phone. Do I want to double my phone bill? Answer: no.
2. Too distracting. Do I really need to play Angry Birds whenever I have a moment of downtime? Do I need to check facebook every ten minutes? Do I need an app that simulates bread toasting? Yes, a gadget-loving co-worker has told me about a few comparison shopping apps that might be a bit awesome, but I'm certainly not going to save any money with them if I double my monthly phone bill! I won't let her trick me, she's already talked me into buying a Nook that I never use.
3. I already have a GPS--that's another practical use for a smartphone that certainly applies to me, but I've already got that base covered AND it was only a one-time fee, technically a gift.
4. I kind of hate people with smartphones. I've found, that having a smartphone around means that you have to google everything all the time, or you just constantly have it in hand for one reason or another. Yes, it's handy it you want to spontaneously go to a movie, or if you're off on an adventure and you need to make new plans, but you can also figure things out. I like relying on my ingenuity, or speculating about something rather than just having the (sometimes dubious) answers right there. If I really, really need the internet, I can call someone, or the library, and have them google it for me. I've done it before.
5. I want my phone to be a phone--and sometimes a clock. That's all I really need, and I barely talk on the thing anyway. I hate talking on the phone and I much prefer texting or IMing, which is clunky on a smartphone.
So yes, sometimes I'm made to feel like a Luddite, but honestly, if all your friends have smartphones, save your money and just make them do all the "smart" stuff you may need. They'll feel proud of their gadget, and you'll feel proud of your bank account.