Well, because I'm a bit of a perfectionist. I have actually thought about just running a front, but of the 50+ forks I have, none of them fit my frame, so I could just get a new frame that will fit one of the forks, but then I should just get the right kind of frame and be able to use both of my brakes. I have a fork that will work with my frame, if I get a threadless stem and headset (because it's so long), but I like old school...

Maybe I will consider a rear caliper, though. Or, just two calipers (maybe old BMX will work?)(I hate road calipers...)

Thanks, jitensha.