for sailing yachts that makes sense. They would use wind for most movement. While in harbor though they want the finer control that being under power allows - they don't need high speed/high power then though. They also don't spend a lot of time in this situation.

I think sailing uses mainly some other kind of energy source.

It makes so much sense. The one's I've seen can be engaged in recovery mode while running your sails, so you can spin the prop and generate electricity. They only get a few hours run time fully charged, but that's plenty for port maneuvers or trip to pick up your crab pots.