It depends on your life style.

I commute two hours a day in no traffic and over two hours in traffic. I don’t want to be stuck in traffic jam or be in car accidents with no ability to call. We also have rough winters. I’ve been stuck in blizzards and storms. I need my phone. I take and receive pictures. I do work related stuff on my phone that is urgent and when I am away from computer. I communicate with family overseas using my phone as all communication is free iPhone to iPhone. I also travel quite a bit. It’s silly of me not to have phone plan.

Having said that, I understand that other people have different life styles like don’t work or don’t go out. But even if you take my dad who is in his mid 80s. He doesn’t work or course but he still drives, shops, talks to people, takes pictures, make appointments etc I would not want him be out and about with no phone plan. And he uses his phone quite a bit although not as much as his computer.