Because it slows you down and makes you think about the basics - composition, light, depth-of-field, timing... and because it's a joy to hold and behold!
Hi everybody! I just bought my first-ever Leica: a mint-condition IIIg

Now all I need is a suitable 50mm lens... unfortunately, finding a suitable collapsible lens (Elmar f2,8 - Summicron f2,0) with decent optics is a real challenge: time has taken its toll and these lens were built using very soft glass. Meaning that they're mostly scratched, fogged, or otherwise impaired. Still, I'm immensely proud of my IIIg and will hang fire until a decent lens comes my way, and can be personally inspected prior to purchase - buying such lens via Ebay doesn't seem to be such a good idea...