Shoulders of quadrupeds vs. humans

Factual Questions
1

When cartoons anthropomorphize quadruped animals they’ll often give them shoulders with a human range of motion to present them with more relatable body language. So you’ll have a cat, dog, or horse that runs around on all fours like normal but can also rub the back of its head, scratch its back, raise its arms 90 degrees to the side of its body, or point straight up. As far as I know real animals couldn’t do this without breaking or tearing something.

But what stops them from doing it, physically? Is it because of the way the muscles attach? Because quadrupeds either have no clavicles or a rudimentary free floating one? Because of the different angle and position of the scapula? If redesigned, could a quadruped’s shoulder theoretically have the same range of motion as a human’s without a dramatic loss in speed or stability?

2

Humans (and other primates) have a “ball-and-socket” shoulder joint involving the clavicle. Quadrupeds don’t want this kind of mobility in their shoulder joint - instead they want stability. So there is a much more limited range of movement between the bones, ligaments, and muscles of the shoulder joint.