Relationships ARE transactional - at least in part. Would you marry a woman who doesn't give you anything, or never fulfills your needs?

> "We should want to make our partner happy."

Theoretically, yes. In practice, most people cares more about themselves than others. This is especially true after the "honeymoon" period, and/or when the partner has disappointed us in some ways (and this always happens).

IMHO, your reasoning seems based more on how things _should_ be, not on how they really work.