I've always thought of it kind of like this:
A vast majority of us have the 5.7L. That's a fair sized engine and will require some time to warm up and generate enough heat to spare for the passenger compartment. When we start our vehicles on a cold morning the thermostat is closed to prevent coolant from going to the radiator and radiating produced heat to the atmosphere until the coolant in the block reaches the temp that opens the T-stat to get rid of the unwanted, extra heat.
Meanwhile, us fragile bags of water have the temperature control in the cab turned over to it's warmest setting. I don't know how much coolant is in that circuit, but it probably makes some difference in the time it takes for the engine to reach operation temp. Also, I suspect that there is a heat exchange circuit that probably sends warming/warmed coolant to the transmission to aid in warming that up as well. I've noticed that while driving when it's really cold and my truck is freshly started, the transmission maintains a lower gear. I suspect that this is to keep the engine at a slightly higher RPM to create more heat and warm both components up faster.
As the coolant warms the heater core and the fan finally begins to push warmed air into the cab, all the things in the cab are going to wick that heat from the air. The dash, seats, plastic door panels, glass, YOU. The bigger the cab.....
Now I know that you're thinking that sure, you have a standard cab so you're truck should be warmed up in no time, but when it's legitimately cold outside, it's a good 20 miles of highway speeds, or more before I would consider my truck "warmed up".
Something else that might be a factor is that on a casual commute, or a run to the store, we're really not working these truck very hard at all. From the reading that I've done on these trucks, the radiator and transmission coolers do what they're meant to, anyone ever see the gauges creep above normal while working them hard (save for a malfunction or failure)? When I've done longer drives in the bitter cold, the heater in my truck is such that I've able to drive in a T-shirt.
As far as warming up my truck from a cold start, I will wait for the radiator fan to disengage at a minimum, winter or summer, then drive off. Bitter cold or snow, remote start as I exit the house, throw my gear inside, brush, scrape, and drive.
Enjoy!