I don't think there's much more to it than that it's nice to have people you're fond of count on you and expect things from you since that's an expression of trust on their part. Fulfilling that trust is just satisfying. The symmetry of requests/fulfillment makes it so that you know you're in a balanced relationship.

Or perhaps there's a Ben Franklin Effect[0] sort of thing going on.

0: https://en.wikipedia.org/wiki/Ben_Franklin_effect