Don't know if this has been touched on yet in this thread, but one paradox with disc brakes that I can't get my head around (other than from a marketing perspective) is this:
Practically, the braking advantages of discs are really only in the wet. Yes, I know a lot of people will disagree with that - modulation, confidence when descending even in dry conditions, bla bla bla. But really, modern rim brakes work so well in dry conditions that all of the minor disadvantages of disks (weight, aero, maintenance, complication etc) together vastly outweigh the small braking advantages in the dry. If you think they don't, I would suggest that's down to lack of experience and a false conflation of the lighter feel of disc brakes with actual modualtion and stopping power. And of course, to the extent that rim wear with rim brakes is genuinely something worth worrying about it's really only if you are regularly riding in wet conditions when grit sticks and wears rims down faster.
So... why do so few disc brake road bikes have fittings to accept full mudguards? (I believe you call them fenders in the States). If it's chucking it down and I want to go riding in those conditions I might actually appreciate disc brakes. But I'd appeciate a dry arse even more..