People who don't have any joy in working with or looking at (older) mechanical cameras probably won't understand why someone keeps track of all the camera's he/she ever owned (and used).

For me things started when I bought my first medium and large format cameras. But it really took off when I quitted smoking and decided to spend my saved money on photography stuff, first books then cameras. Expensive? Not at all, just know what to buy and when to sell it again.