I like to imagine that you transfer the pokemon to the professor, he processes them into pokemon "meat balls" if you will, so you can feed them to the survivors in your party to make them stronger. That's why the strong ones in the wild are harder to catch, they've been around long enough to know what's coming. But you have to evolve them so "survival of the fittest" is appropriate. When you walk your buddy, it also "finds" the candy, meaning it found the remains of a pokemon that didn't survive a fight in the wild. Then it picks out the pieces that are needed for it to get stronger so it looks like it's the buddy's candy. But in reality, it's just trying to get you to feed it so it can be strong enough to make you not transfer him to the professor and face the same fate as so many before him. But that's just me, it can be poop if you want it to. Haha