To me service is something that you put your heart and soul into. In some cases risk your life for. You spend years in training to achieve. That you vow to do to the best of your abilities. That you only do if the task and person meet your values.
Sex can be a service also if you spend time and serious training learning how to use your mind and body to please someone else. If you keep your body and mind fit enough to be a good sexual partner almost a therapist to your lover. If you allow yourself to be intimate and honest with them. To trust them. To cleave to them, as it says in the marriage vows.
Dominance/control are about more than a bossy, hauty attitude. They require an enormous amount of energy and dedication to achieve correctly. You need an intimate understanding of the people involved in the dynamic. You cannot be stagnant. You need to grow as people and as a dynamic. Because power is a dance, not a chore. Each soul is a responsibility to each other. Whichever side of the whip they are on. To use power badly is to be a brute. Not a dominant.
A chore is something anyone can do for you. But someone who does it with love and dedication for you is serving you. And the bettering of their skills, for self love. The craftsmanship of the tasks and the self-responsibility of improvement and self-pride in doing things right is service. For not only the receptor but also themselves. For honour. It is about nurturing the body and the soul with their positive attitude and caring.
And it is about having arrived at a certain place in the journey, reaching back and mentoring those coming up. While you still sit at the feet of your elders and betters, you need to start passing the lessons on.
This is all service if done with a heart rather than just a body going through the motions.