That's a question that actually bears some looking in to. Since you say that you're not quite 50 (I'm in my late forties as well), you're not old enough to be the typical techno grouch. And I thought I was a meanie for making my kids wait until they were 12 before I'd let them have cell phones. My daughter being younger found it especially onerous as she had to endure her brother having a cell for a full year and half while she did not.
I’ve never been a fan of cell phones, even before they took pictures/movies. What finally put me over the edge was at my Grandmothers house last Christmas. My two nephews, who are about 7ish, were sitting about six feet from each other, texting each other, and they did it for a long time. It didn’t make me postal at the time, but it did plant a seed. :-P
We have become a world where not only do we not interact, but we don’t even look up to see the world anymore. I do have a cell phone, but when I leave the house it stays at home. If someone needs me, they can find me. :)
As for your own cell phone rule, I respect you for it. I would be the same way if my kids weren’t already out of high school.