I see too many angles, too many possibilities, and my eye picks up more information than I can possibly put on a piece of paper or canvas. The possibilities and information enter my brain too fast for drawing when I am someplace new. If I care too much, how can I possibly mark it all down?
The camera helps me compose. It helps me take notes. Is fast enough to go through many ideas quickly. I lets me take the snapshot so that I can leave it alone; let the pile of photos sit while I let time decide which composition, which spot, which view, which feature is important.
The camera is a way for me to draw on my mind before I start drawing on paper.
This explains why I take so many pictures of the same thing.
It also explains why I can only reference my own pictures. Using someone else's pictures shortcuts the initial drawing experience.