I haul so much crap back and forth from the cabin, that I need a full cap as well. Plus, I hunt so I keep my dog kennel in the back of my truck 24/7. In the summer time, I can open the side windows in the cap and give him some air when I run 5-6 hours to the cabin too.
I admit, it throws a grampa factor into the truck looks, but it's pretty practical.