My observation around here has been a limited number of service stations which do propane refills. With that said, there are three within a 5-10 minute drive, as well as a dedicated propane distributor. As others have stated, it would seem the lower volume service stations have gone to 20lb tank exchange, as propane BBQ refills likely make up the bulk of their business. I would speculate it doesn't make financial sense for them to keep propane dispensing equipment available, in addition to trained staff to operate it.
I wonder if the apparent decrease in service stations which dispense propane has anything to do with a change in propane/CNG-fuelled vehicle numbers?