It's odd that the passenger side wasn't the one to crumble? Since it's on the right side of the crown in the road where all the s_it lays? Mine was the same way. I replaced both sides with new units from Dodge, they weren't too bad (at least for the dealer part cost) I think like $20 each. They were basically raw, had to be painted and primed prior to install.
To the question: do you really need them? No. Why are they there? To help fend off junk from the road getting between the pad and rotor = could cause damage to both, and to help reduce water on the road from spraying up on the hot rotors = after a while warped rotor. MHO