That's right. They're using just about every other type of vehicle imaginable including pickups with caps .Every once in a while you'll see a USPS unit picking up in town boxes and other utility work but that's about it.You're saying FedEx and UPS no longer use Sprinters in your area? The Sprinters you used were inferior to the current models. Or are you of the opinion companies never learn from their mistakes and make improvements? And their payloads are higher than Ford and Chevy vans. Ford got rid of the Econoline because it couldn't compete and brought in their Sprinteresque Transit.
Now out there in Flatland Kansas where surface water ( on occasion when there is some) has to go looking for a place to run to one might work but when you had to take them out onto logging trails. abandoned strip mines gas line right of ways etc they just couldn't hold up.Not to mention always getting them stuck in addition to the nearest dealer 90 miles away and the people who had them were tired of getting mauled for parts and labor.
I know a guy who owned a food company. Had 3 of them . One by one he sold them off and replaced with Fords as quickly as he could find a buyer for them.