No one has mentioned this, so I figured I should...
Could it be that Dodge doesn't put manual hubs on our Cummins powered trucks (& thus, all their trucks, as most 3/4 & 1T Dodges are Cummins powered) b/c the torque of the Cummins would destroy virtually any manual hub made? As an avid four wheeler for many years, I known that the weakest points in most 4x4s are the manual hubs. In fact, one company sells a product called "hub fuse" that is designed to break before destroying your hubs. Given the ridiculous torque even the earliest Dodge Cummins trucks had, a full-time hub seems like the most logical solution.
Don't get me wrong. Axle companies could build a hub that would stand up to the Cummins, but it would be prohibitively expensive. Frankly, early locking hubs weren't created to save mileage, but to reduce wear & tear on the front axle. Most of the parts then weren't designed to provide continuous service. The stub axles rode in brass bushings or on tiny needle bearings. The u-joints were tiny. Given that both tires turn the same speed most of the time on our Dodges, very little wear occurs in the differential itself, except on the 2 carrier bearings & pinion bearing. The stub axles ride directly in the same bearing that supports the frontend. Now that a substantial front diff is used (instead of a weanie Dana 44 or the like), it should last as well as the rear diff.
In my book, the only reason to consider manual locking hubs would be if you installed a limited slip front differential, such as a PowerLok, Auburn, etc.