The move to hydraulic disc brakes made cable routing far less of a problem and easier to have it inside the frame for a better cosmetic appearance. Originally the disc brakes were considered important only for tandem bikes where the rider weigh was doubled. It would be advantageous with sewup tires where it is possible to have a problem with heating up the rims and softening the rim cement on a long steep descent. Now it is a good way to get people to spend more for a new bicycle.
My 2001 Trek 5200 has caliper brakes and they work perfectly well at slowing and stopping the bike.