I do it outside as often as I possibly can. Unfortunately, that is becoming a lot less frequent, as now I live in a city and not in the middle of nowhere, like when I was a teenager/young adult. In fact, it used to be that outside was the only place I could do it. Thinking back, I probably thought that I was more obscured than I really was.
That said, I did get really lucky recently with a couple of friends that wanted to go hiking at (I kid you not) Poo Poo Point Trailhead. All of us found a secluded spot and there didn’t seem to be many people around. As such, I managed to get knotted and filled up partway through the hike! It was very convenient, too, as we all needed a break from walking uphill for so long.