I as well see no logical reason to move away from 5er, my wife and I are in our 70es an our auto leveling system makes it a one button job, even if I have to put pads down it's not a ruff job at all. If you have a DP you still in some cases have to put down pads depending on the camp grounds an have to unhook and hook up your toad, if you have a 5th wheel you still have to hook to the 5th wheel so I think that's a wash .....
Driving a DP the minute you pull into a repair shop all they see is $$$$$$$, if you pull into a dealer with your pickup they only see $$ not $$$$$$$ ......
Like the OP I also see the cost. A new truck 60K, a good used truck 35 to 40K, a new nice fiver depending on the brand low end 50k high end 90K. New DP in the approx same size 250 to 500K. again as with the OP the DP loses hands down.
Lastly I had to wonder at the OP that stated the only time they drive there pickup was to pull their 5th wheel when they go camping. So I would think the only time they drive their DP is when they go camping as well ....