Harnesses are redundant, too. About a year ago, I watched someone get half way up the wall and fall, only to have her harness come unbuckled. Fortunately, the leg loops kept her suspended and she just down-climbed and fixed her harness.

(Part of the problem in this case was not understanding how the mechanism worked, which is not a good idea when it's the mechanism that stops you from falling 30 feet onto the ground.)