We have clover mixed in with our grass as it's much more drought tolerant. We still have to mow it. Even the special golf course clover which is very low growing has to be maintained and mowed.
We have other ground covers that don't need to be mowed but they are in borders and we don't walk on them. One border is a mixture of periwinkle and sweet woodruff. Occasional walking on by the dog hasn't hurt it. And, yup you're right, rock gardens are a lot of work to keep weed free. Both periwinkle and sweet woodruff can become rather invasive. Be sure you research your ground covers thoroughly if you think of going that way.