I bought my first 35mm camera, a Canon AE-1, because I was already familiar with it. My mother owned one, and I had used it on several occasions. So because I was comfortable with it and because I enjoyed its limited automation, I bought one. It's worth noting that about a year later I bought an A-1 because I was so fascinated by automation that I wanted even more. And then maybe a year after that I bought my first medium format camera -- a Yashica Mat 124G -- which was the first camera I bought specifically because of its film format.
The Mat was the first camera I owned that had no automation, thus it was the first camera that I owned that became a useful tool as I learned about photography. And it wasn't too much longer after that when I decided I needed a manual 35mm camera also. So I bought a Canon FTb. That camera was really responsible for me learning the inverse nature of exposure and how it depends on three principles of exposure: film speed, shutter speed and aperture value. Not much longer after I bought that old FTb, I bought an original F-1 and that camera was what really set into stone my attitude toward cameras that has held ever since then. I eschewed automation and still tend to prefer this attitude with respect to photography.