RE: How many park flyers have YOU seen?
Let's not forget that I could be flying a small electric plane under 100 feet in altitude within 200 feet of you. If you are on the other side of a building, trees or some ohther site barrier you would probably never know. I could even be on the other end of a football field flying a plane 200 feet in the air. If you don't notice me, or don't happen to see the plane in the sky, you could be in plain site and not see.
These small electrics are typically very quiet and somewhat small.
After all, isn't that part of the attraction of small electrics?