Performing touch-and-go deadlifts doesn't mean that you stupidly bounce the weight. You must maintain control. The benefits include:

1. Developing more eccentric control to build more strength and muscle.
2. Building grip strength.
3. Using the touch-and-go method more effectively trains both sides of the rep (concentric and eccentric), meaning you're essentially doubling your time under tension.
4. Touch-and-go demonstrates an implementation of the stretch reflex and a much more dynamic muscular effort than complete stops. They're better for cultivating athleticism and the learned explosiveness will transfer over to bigger dead-stop lifts.