I was in Rome many years ago and while I was there I took a tour of the Vatican. At the time I didn’t really understand the influence the visit would have on me, nor how what I saw would become an ingrained part of the way I take pictures.
While on the tour I noticed that in every painting someone (usually a young woman) would be looking at the audience and the eyes would follow you everywhere you went in that room. I mentioned this to the tour guide who explained that in this period it was normal to have someone in the painting referencing the viewer. I liked this idea a lot. Now, many years later, when taking pictures of people in public I still prefer to have someone looking at the camera. It may be a tick, but it is something I consciously do, and the images I choose to display invariably have someone looking back at the viewer.
EOS RT, 50mm, Fomapan 400 B&W film, developed in Rodinol (it was all I used at the time, which is why I remember)