The slipper clutch is a weak link put in to save your tranny/diff/clutch/drivelines.
When your truck is in the air, and all revved/spun up the drivetrain has a lot of momentum. When you hit the ground, the tires instantly stop spinning, the engine still wants to move forward, instead of smapping something, the slipper is supposed to give and slip -- just a little bit so you don't break something in half from the shock of the sudden stop.
If your tires were all ballooned out, and you stopped them suddenly you could break anything from a connecting rod in the engine to dog bones or diff gears.
That being said you don't want it to slip on take off, only on hard landings/hard driveline shocks.