Ford has locking hubs in its unit bearing set up. Never saw one apart but if they can do it why can't Dodge make them that way too.
... because it will
most likely be way out of warranty before the bearing gives it up. Then the dealer can sell you parts AND bend you over the tailgate on labor. It's cheaper for Dodge to get the axles that way from AAM, or previously, Dana, the majority of the market is "satisfaction-now" buyers, meaning they want 4x4 when they pull the lever, no conditions allowed, no time to wait or work for it to engage, no reason to get out in the cold or hot and engage the hubs. Ford still recognizes the small segment of the market that wants features that make the truck run more than 100k miles, and accomodates them... . somewhat.
I went to free spin kits on my newer work trucks, as I got tired of breaking CAD connectors, broken axle shafts, broken vacuum lines, and bearings giving it up at the worst possible time. Since then, I've only had a small issue with my Dynatrac's, involving a snapring, but that was an easy fix without having to take the whole wheel off. I considered myself very lucky to get 100k out of a pair of unitized bearings. The old '91 and '93 are running on the original bearings, but I've put several sets in all my 2nd gen trucks, and finally needed some in my '03. The '06s and '07s haven't gotten to that mileage yet, but I'm anticipating.
FWIW, the Spyntec/Solid Axle kits are really nice. The seals are recessed, as well as the ABS sensors, protecting them from brush and heavy mud. Those guys are pretty good to deal with, too. Dynatrac's are good kits, too. Also don't overlooked the Yukon gear set, if you decide to go that route. I don't necessarily think they're priced very well, but they're made well.