Question about attaching rear fender flares

Why not just replace the "spinning" nutsert with a simple nut and bolt? It's gonna spin again by time you get around to having to remove it anyway right? I mean other than wanting to stay original. Is there anything that makes the nutsert better than a simpler fastener i.e. - nut and bolt?
If you don’t have the linked hardware in post #4, and you have access, a bolt, nut and couple washers would be fine. I’d use a lock washer on the nut side, or a nylon locking nut.
The reason that there are nutserts there in the first place is that there is not access to the back of the fenders. Without cutting holes in the Jeep, you can't get to the back to use nuts.