I think we need to understand human to human relationships before we can understand our relationships with other species. Family aside, we have friends that actually do things for us and make our lives easier but we also have others that we get no tangible benefit from other than enjoying each others company. They work when it makes a pleasant experience for both. Which comes first, feeling good about making someone else feel good or feeling good ourselves? I referred to two of the barn cats as "my friends". Why not? We are always glad to see each other and we all get something out of it. The same with horses. Horses may have been domesticated to make our lives easier but primitive man may also have become "social" out of necessity rather than a need for social contact. Once a species becomes social the need remains regardless if there is a physical need for it.