Why? Simplicity and the best braking in all conditions. I wish my 1x1 had the rear disc brake tab (wanna trade?). I've got a rigid disc fork up front and it makes winter riding a lot better. At freezing temps around here the streams are still flowing which means iced up rims. Maintenance? Yeah right. Nothing compared to a rim brake. I bled my brake once in year and that's because I broke the lever/reserviour body and had to replace it. On the other hand, replace your cables once a year, multiple brake pad changes and adjustments for cable stretch and pad wear on the V-brakes, cleaning the grimed up rims, etc. The only bike with less maintenance than a rigid SS w/ hydro discs is a brakeless fixed gear.