I would think the main reason for no sound is the inability of adding it to the video. Post production can be difficult for many.With the Mavic pro it was amazing. Fliming my sons rugby games. You could hear everything but the drone. The audio is being recorded where you are.
Same with get togethers and just fliming a mountain. You hear the wind, the river that your over. The waves.
I guess I don't understand why people are ok with drone videos that have no sound. You just add some music to it.....your missing the other part of what is going on around you. Sound!