Ok I am going to have to ask the stupid question of what is the difference between a tow strap and a recovery strap???
A tow strap doesn't stretch, a recovery strap does. So...when you jerk someone out of, say, mud, the recovery strap stretches, storing some energy, then that stored energy helps pull the jeep out.
Also, when it stretches, it's less of a shock than if it was a non-stretching tow rope.