I don't think I know anyone who's using a single plan, though I'm sure they're out there.
But yeah the misc fees are annoying, especially if you ever travel or call overseas.
Edit: Wait, are you implying that Mint's pricing is $35 total, not per line?? No matter how many lines?
Setting aside unlimited plans for the moment: You can get 5 GB of data per month, which seems pretty generous to me, on an MVNO for only $15 per line.
The family plans (whether on big carrier or MVNO) get cheaper per line while going up in total price. But yes, not everyone needs unlimited.
To his point, however, I acknowledge that saving a few hundred dollars per year just isn't worth it to many people when they can walk into an AT&T store, sign whatever the salesman puts in front of them without thinking about it, and have the salesman take care of all the required setup.