I love the look of a well loved pipe, with a patina of smoke stains around the top of the outside of the bowl and a little cake oozing up from inside and flowing over. That said, I do have pipes that I try to keep the rims as clean as possible, but this is not the norm.
My first Becker was a Danish scoop, blasted with spectacular smooth grain around the rim. I kept it as pristine as possible, cleaning and buffing that rim after every smoke. The pipe smokes like a dream, but keeping gunk off the rim the way it is designed is impossible. Now, I just smoke it, and let the cake creep out all it wants. It actually adds a beautiful nuance to it. But, I don't ever plan on selling any of my pipes. So, I could care less.
When I am hanging out at The Briary and someone comes in and asks about how to keep a rim clean or hesitates buying a pipe with a spectacular rim, the guys all just start laughing at the guy. "It's a tool." Buying a pipe designed to smoke well and is beautiful and wanting to keep it pristine is like buying a new pickup truck and refusing to haul anything because you don't want to mess up the bed.
But, on the other hand, some trucks are probably better off on showroom floors than in the field. If you happen to have the luxury of having a showroom and enough other trucks to keep you working... YMMV