Are we suggesting non ESA shock are too cheap and to bother protecting? Of course not.
The bike creates a low pressure area ahead of the back wheel. Muck flies off the wheel then gets sucked forwards splattered then out all over rider's legs. Mud Sling is worth having for that alone. If the TUV shovel thingy is fitted even more crap get thrown forwards.
Check out a bike with a hugger fitted. You'll see crud all over the top of it so clearly its not stopping the mess. The mud sling works. A wrap around hugger like the Britten 1000 would work even better.