Bear in mind the issue of space.
First, if we all decided that moorings were cheap and great, and everyone in Annapolis used a mooring, I doubt there would be room for more than 15% of the boats. Sort of like if all apartment and townhome dwellers decided they wanted land. The math does not work.
Second, in crowded areas, boats on moorings are a huge pain to transients trying to anchor. In some areas, good anchorages have been ruined by "mooring queens," or simply by a few owners out to save a buck. Again, what if we all decided to plop our boat in the middle of a favorite back creek?
In virtually all states, navigable waters are a free resource; the marina does not pay for the land they use for docks and the mooring does not pay to use the middle of the creek. Both seem a little unfair, when a large marina ruins a favorite cove with docks and balls. But we all have to park somewhere, so we accept the evil. We gripe when mooring is restricted, and it isn't always regulated wisely.
So while the OP has an interesting statement, I think closer examination is required before we call it a virtue. Like camping out, it works when only a limited number of people do it. After that, it becomes a Hoverville.