There's an added benefit too. The longer the teather, the more Earth's magnetic field will generate a current on the teather. Its good because that's exactly where the electricity will come from to power the elevator as well as nearby countries. I'd heard Nasa did an experiment with teathers once and it burned up the wire they lowered from the shuttle - very long wire, too much current. But a wire is one thing, and a serious cable is another.
If you are talking about the TSS, it failed and had to be cut loose because a bolt was too long and bound the cable in such a way, it could not be retracted.