For business or special occasions, I have a white dress shirt that I wear with black or charcoal slacks, and a beige dress shirt that I wear with brown slacks. No amount of other shirts would ever diminish my need for these shirts.
I have Polo brand pull-overs for a casual night out. Now, if you've never owned an actual Polo brand shirt that didn't come from the "irregular" discount store, let me tell you, the cut is exquisite, the fit and finish amazing, and wearing one makes you feel like a million bucks. Of course, a $5 t-shirt will cover your torso just as well, but the experience just isn't the same. No amount of t-shirts would diminish the returns I get from my Polos!
And so it is with pipes. A cob might smoke similarly as other pipes I own, but that is not the extent of the experience. When I am in the workshop, I might smoke a cob just as I will wear a t-shirt. When I want to look sharp and feel good about myself, I will reach for a pipe with refined curves and lines, fit and finish. I have "dress pipes", and "casual night out" pipes, and no amount of pipes added to my collection would diminish the returns I get from these pipes.