"Rustication can be a cover-up..."
I believe that is the reason the technique was developed in the first place, to cover-up flaws in the briar which might otherwise render a pipe unsaleable. Further, rusticating tools can be simple and inexpensive (especially when compared to sand-blasting equipment), thereby reducing a pipe-maker's overhead and the individual cost of manufacturing such a pipe.
Personally I view each as separate and distinct finishes, and like them both if well-executed.