Im not sure what planet you live on. They absolutely will. Cattle and deer are dumb. As a cyclist, I doubt you ever leave the city and actually think a significant amount of people buy them for looks.
Anyway, I grew up in a rural area (outside of Texas) where grille guards could be useful. Didn't see many grille guards back there. I even (briefly) worked at a farm before, literally shoveling manure.
I've lived here long enough to observe that grille guards are far more prevalent here than they are in other places, even other places where grille guards seem appropriate.
Also, as a fellow Texan, you're dead wrong. The majority of the people who have those have them because they have ranches and do need them.
Given that I live in central Austin, I find it hard to believe that most drivers I encounter with grille guards need them because they have a ranch. That would imply that many more people have ranches than I believe is true. Plus, I grew up in a rural area outside of Texas and rarely saw grille guards, even on farms.