Every organism on the planet needs to behave in particular ways in order to survive. For some the behavior is more complex, for others it might be moving in one direction with their mouth (or whatever it is they have that allows nutrients in) open. Even microscopic organisms will change their behavior based on whether or not they are reinforced for a particular behavior. They may be limited to simply changing direction, but nonetheless, they will if a behavior is not reinforcing. There is a beautiful flow of experimental behavior that allows single or multi-celled organism to discover which behaviors work for them. The definition of what works is will vary between different organisms and may even vary for a particular organism depending on other conditions; the time of day or what they may have had or not had for breakfast, for example. Guiding these behaviors is a built-in reward system.
That we have taken away the need for our dogs to perform certain behaviors, specifically foraging or hunting, does not mean that we have taken away the reward system in place to ensure that these and other behaviors continue to be performed. Some people like to say that dogs need jobs or need to work, and I suspect some will say that I am splitting hairs when I choose to avoid using these terms in relation to my dogs’ behavior, and no doubt were my border collie able to talk we’d have some lively discussions about it, but I don’t think of asking my dogs to perform certain behaviors in exchange for a treat or toss of a frisbee in terms of them needing a job or requiring that they earn their living. Instead I prefer to think about not letting the perfectly good reward system in their brain go to waste.