Some of the dogs in my pack really like retrieving balls, especially from the water. There is nothing more joyful than watching dogs charge in to the waves after a ball and then surf out. I never get tired of watching that.
However some of these dogs that enjoy ball retrieving take it to unhealthy level. The ball becomes their heroin. They cannot function if there is a ball in their vicinity that is not in their mouth or under their control. They jump all over the human trying to throw the ball and get into resource guarding fights with any other dog that comes near their ball.