They did when I drove through there a year ago. Same as literally every other place along the Interstates. *shrug*. I wouldn't buy it there, either, though. Just like I wouldn't fill my Volkswagen up with the OTR trucks (unless there was no auto diesel pump available, which I have run into a handful of times over the decades of driving diesels).
The truck stops would be going through FAR too much DEF to JUST have it in the 2.5L jugs. Otherwise, you'd see mountains of empty jugs everywhere. They don't even use the 55 gal drums. It is delivered in a truck just like fuel gets delivered, although there are the big cube containers with pumps they can also deliver. That's what most small fleets use, and those get refilled.
The only SCR equipped diesel I had was my Sprinter, and it used so little DEF that it is a complete non-issue to fret over a few cents savings getting it via a pump dispenser. It's cheap. It's universal. It's everywhere. I also like the fact that you get to break the seal on the containers, so you KNOW it hasn't been left open somewhere and vented improperly. The concentration is a key component.