If you have been in the auto business long enough you surely remember the original 4x4 which implied a locking transfer case, low range, free wheeling hubs. Ideally you wanted the 4 wheels to be solidly connected in extreme applications.
When you shifted the transfer case to 4 Low Lock...you were looking for fun/trouble, and hopefully had a few friends in the vehicle with you, and a shovel or two, and perhaps even a winch.
As an aside Toyota has a totally cool off road cruise control for its vehicles that still have a frame and an old fashioned transfer case.
It was more money, raised the vehicle off the ground, added weight, and additional mechanical drag/friction (differential in front, transfer case). At one time every ,manufacturer had a brand name for their 4x4 set up on the premise that one was better than the other.
Pick ups continue to have the classic 4x4 set up, although the transfer case shifter has morphed into a knob in the dash. Much easier to shift than grappling with the old school shifter on the floor.
How did 4x4 evolve into AWD and become so pervasive in Canada?
1- Get rid of the Low range in the transfer case, now its smaller, lighter, and can still power the front wheels, or the rear wheels in a FWD platform. Obvious that by omitting the Low range, the off road/deep snow capabilities have also been removed.
2- Lets use the ABS and Stability technology to control the power at the respective wheels. Instead of a limited slip differential in the rear, the brakes are applied to the spinning wheel to reestablish traction. Agreed it makes for a smooth flow of power to each wheel.
3- Lets get rid of the transfer case (on the premise that there is a differential in the transfer case to compensate for the difference in the front and rear). The technology is keeping everything uniform by applying the brakes as required.
4- No transfer case...what do we do? Simple we need to redirect the power to the front, with a simple lets call it a transfer case with no differential (just a clutch pack just in case). Lets run primarily on 1 axle similar to 2 High, and have the technology decide when the other axle engages and at what rate.