I'm not sure that anyone is worried, rather they're attempting to strike a balance between lift height, fender trimming, and less backspacing. Obviously, the goal is to avoid hitting the control arms, allow for good tire stuffage, and to provide stability to a lifted rig.
I do think one can extend the tires out too far using too little backspacing. However, I think it really depends on the lift height. Besides the funny look, you can prematurely wear out ball joints and bearings as you appropriately mentioned. Not only that, it usually negatively affects steering. And some states do enforce the law concerning the tires and fender coverage, so I can only assume some Jeepers here prefer to be responsible by following the state statutes.
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