Are bumper gravel guards really necessary?

[Gibson]

I'm making the jump from an old beat up step bumper to a sport bumper on my '78 longbed and I had to buy all the brackets and whatnot too because the sport brackets and step brackets are different.

One of the things listed in the LMC cat are the "gravel guards" which I went ahead and bought, but now I'm wondering if I even really need them. Do they keep gravel from being thrown by the wheels onto the bumper or something? When I try to mount them, they interfere with the tailpan a little bit and I don't want to have to mess around with modifying them if I don't need them. Any advice appreciated!