The old coke bottles were returned and actually refilled by the bottlers. (This was before recycling as we know it today). My point being that the glass used for making bottles is different and softer than glass used by "quality" paperweight makers. When bottle glass is used to make paperweights (and many beautiful weights have been made with bottle glass) you can expect basal wear, as well as surface scratches to occur MUCH easier than it would be expected with a harder glass.
As a longtime collector, the reason I personally want to see the base of a weight is not to see if there's a wear ring, but to see how the base is finished. Is it flat or concave? Is it polished, ground or rough? Is it symetrical? Is there a pontil scar? Are there any other identifying marks or characteristics? You can have a Clichy with no wear to the base, just as you can have a Perthshire that does. It depends on how often the weight was dragged across another (harder) surface, or possibly repolished.