I agree that the "something in return" doesn't have to be from the other person in the relationship. For example, a doctor attending a patient is employed by the hospital, not the patient; she gets nothing from him. Still, it makes sense to view the way they relate to each other as transactional. The patient wants to get well, the doctor wants to get paid.

I agree that people can derive pleasure from helping a specific person. But it's not normally the whole story. What they also want is expressions of gratitude, that person's company, etc. For example, your parents may want to help you, but if you never say thank you, call them or see them, they won't be inclined to help you nearly so much. Human beings are social animals. The "helping" is not the whole, or even the majority, of the story.