That's interesting. I wonder why? I would figure the security problems, lack of a lot of extras, and probable slowness because of increased OS complexity (to the point it was supported) would make it less useful than many of the simple half-dumb phones out there.
The security problems would trump most other considerations for my for a modern era smartphone of that vintage.
I have one that I use occasionally. It's currently charging in the kitchen.
Though most of the stock apps on it don't work anymore, it's fine as an actual telephone, address book, very basic camera, and a few other things. A lot of the apps on it are no longer available, and since the App Store app is so slow as to be unusable, they don't get removed.
Safari works, but most sites look like they've had their CSS disabled. So it's kind of like WAP days.
It's a good phone for banging around with in uncertain areas, or where you need a phone that you don't mind getting wrecked.
In my opinion, the form factor is still unsurpassed. And it feels good in the hand -- weighty and assuring, but small enough to not get in the way.
The thing I use it for most, though, is the music player. Somehow it sounds better than the newer iPhones. But then, I also think the Shuffles sound better than the newer iPhones.
I understand it can be used for those things, it just seems like it comes with a fairly hefty downside also. You can get a Moto E5 prepaid for $40-$50 if you get it from an AT&T store and sign up for a $15-$20 a month prepaid service (likely cheaper than adding it to a plan anyway), and that's a fairly modern phone and includes a FM radio.
It's not free, which I understand, but it's also not nearly as likely to be immediately exploited by some of the various problems older phones have had (SMS hacks, browser exploit hacks, etc).
The security problems would trump most other considerations for my for a modern era smartphone of that vintage.