Why do dogs enjoy fetching things?

is there some biological reason that they get pleasure from bringing a tennis ball back only to go chase it down for long periods of time?
Dogs are genetically predisposed to chasing after objects that move [3]. This is a deep-rooted instinct and not a learned behavior [1, 3]. Some dogs enjoy fetching and bringing back objects because it's part of their genetics [3, 4]. Retrievers, for example, are selectively bred for the desire to retrieve things and other breeds are developed to hunt small game or herd livestock [2].
The reason dogs enjoy fetching things is because they are genetically predisposed to chasing after objects that move [2]. According to scientists, the earliest domestication of dogs may have come as a result of hunting [3]. Early humans could have bonded with wild canids and ultimately had them assist in hunts of large prey, thereby utilizing their impulse to track, chase, and retrieve [3]. Additionally, dogs are naturally curious and will orient themselves toward something that interests them [1]. If they see something move, they will chase after it [1]. While the exact reason why dogs enjoy fetching and carrying objects back is not known, it is believed to be a variation of a natural canine behavior called "prey-carrying" [2].