Name another sport specific movement that is hyper-focused on stressing an already weak joint, yet that movement is critical to the very essence of a win, or loss, in each game.
% wise, how many big league pitchers throw their arm out?
It's about mechanics, it about not having a strength imbalance in the 5 main muscles in the rotator cuff.
Kids rarely get taught at a young age how to separate thumbs down and the elbow above the shoulder, pulling an pushing off the mound. When you get that part down, with that comes arm speed.
One thing I would add for anyone who has a kid who pitches. You should have them do what is called "arm hangs."
When they're done working out, throwing a bullpen, or throwing in a game, they should then find a small fence or a bar and just hang down with their feet off the ground. The gravity forces the blood that gets pooled in the shoulder to evacuate the area and leads to zero sore arms.
When they don't do anything, it causes the blood in the arm to "pool", kind of like scabbing, and hence you get the really sore arms. When they throw a lot and don't use proper aftercare on the arm, the blood rushes to the traumatized area of the shoulder and blood pools there as if it is rescuing the area. Then the kid can't even pick his nose the next day.
Then a nice 20 minutes with a Pro-Ice or just a arm pack and they are ready to go. You can even do what is called a "shake-out".
If you take care of their arm,, their arm will take care of them.
FWIW