Modern pickups have 8-10 speed transmissions. They do a better job of keeping you in the power band.
In addtion, no heavy duty pickup comes with a manual anymore, but the ones that did years ago, de-tuned the engines in the manuals, so people didn't burn up the clutch. Modern Diesel Heavy Duty pickups only put their full 1000 ft/lbs to the wheels in 3rd gear or higher, something they can't enforce in a manual. Also, in most manuals (granted, its been a few years since I drove one) with turbos, pushing the clutch stats unspooling the turbo, where in most automatics, it does not. (since its knows your shifting, and not just coasting)
Yes, these are all related to driver skill, and a skilled driver will not cause problems. But I wouldn't want to warranty the systems on an 'average' driver..