In my case I would be protecting the pipe from being knocked over by the cat, the dog, anything that could cause it to suffer some unfortunate fate. I no longer have young children and I suppose when the time time comes that I live alone, which is eminent, then that would eliminate any worries, as presumably, the pipe would stay where I left it. I guess I've seen too many "accidents" over the years having three children. In my case, if it could happen, it did! For me, if it came with a case I keep it in the case.
Also, my most treasured meers are intricately carved figurals with small details that could easily break off if the pipe should somehow fall from a rack. It is just safer to keep them in the case, for me.
I agree with Sable's approach that those pipes would never, ever, look as beautiful if they were not cased over their lifetime. And, also agree with what he says about our collections and attitudes towards them.