No, not all dogs are bred for it. Mine is a malinois x canaan dog x GSD with a drive to work and work. With agility titles under his belt, IPO3, obedience I wanted something new.
Dogs are not supposed to be couch potatoes. Dogs were made to do a damn job and a dog like mine that NEEDS a job will be worked. If he didn't want to do it, I wouldn't make him. My bitch a GSD from working lines has no drive for sports. Her workout is running along while I cycle and that isn't for long either. She is lazy, she doesn't do anything to keep her busy. My malinois mix on the other hand is 8 years old and can run rings around pups. I want him to slow down but he won't so I make sure we keep him active and enriched.
A weighted vest is no different to a saddlebag. When we go on a camping trip. my dog has his own bag. He will carry some water, food and other useful things we will need on the way to our site as well. This makes him work that bit harder. Work hard, play hard. Weighted vests are good to condition a dog. It is like putting a weight in a backpack to build up muscle in athletes. Dogs are supposed to be athletes. You can stick with your pampered pooch and cry about aboose but I will continue to treat my dog like the athlete he is. I aint a fur mommy but you can bet your ass my paycheck goes to my animals before myself.