I actually have done it a fair amount. Here are a few examples
-- On the nude beach, back in the dunes. Every summer or two there is a couple who, after chatting awhile express interest in see how an uncut cock works in real life. I'm always happy to demonstrate, soft and hard, and to let them try for themselves. This has happened all my life.
-- In the steam room at the Y as a prelude to getting a hand or blow job. That was a while ago.
-- In a few orgies, I had fucked all night in all sorts of combinations, with condoms, basically edging without cumming. Toward the end, I would ask a favorite partner if she wanted me to cum all over her. People close would hear, or notice and a little crowd would gather, cheer us on as we both stroked toward orgasm, and applaud as I pumped rope after rope of semen over her.
-- With my young naked wife on a rock in a cove in a Canadian state park. We were both jerking, then she came and then held my balls as I came. When I had finished shooting, I looked up and saw the faces of 6 or so hikers looking down at us. It turned out the the trail had run right along the edge of the cliff that was right above our rock, maybe twenty feet up.