I can understand why cost might be factor in not making it worth getting a smartphone, but given that we're all people who play games and use the internet, I'd find it pretty hard to believe that if given a smartphone for free with a free data plan, people would just use it as a dumb phone.
I'd be surprised if either Spoon or Mongoose were arguing anything to the contrary. If I got a smartphone it would cost me between five and seven hundred dollars for two years of operation (varying with fancy-ness of phone), and that's only the cost of the phone plus the data when it's bought in conjunction with my family's plan. Which brings us back to this:
Yes, they're expensive, and it's totally legit to not want to get one because you don't think you'd get your money's worth out of it.
Personally, I've been tempted to get a smartphone for the past six months or so. All but one of my courses this semester rely on group work and we use facebook groups, github, and piazza to keep track of our work and communicate with each other. Meeting in person or staying at home isn't realistic when we all have to juggle work and classes, and I'd find having some way to check up on things when I'm not actually in a position to get work done supremely useful, not to mention the general utility of internet in my pocket.
Obviously, I'm at a loss to give any reasons, other than novelty, why Mongoose would be willing to spend the money on a smartphone if he would only end up using the data features on rare occasions. No doubt he would be glad to have it on those occasions, but it just wouldn't be worth the money.