I think that doesn't treating your deck like the holy grail does not equate to treating it badly.
Like Glitterbird said, i treat my decks well because if damage one of them real badly i may never get the chance of getting another copy, because most of my decks come from abroad. But not because i think they'll be hurt if i shuffle them the wrong way.
I think deck are meant to be used and abuse when they are doing their purpose - reading, being studied, helping people etc. Worn decks feel good, like they have a story to tell, like old companions with some battle scars.
But there's a limit. Letting your decks be damaged just because you can't care less... it's a matter of view. Some people can easily get new decks... other people can't. I agree that one shouldn't treat his tools of trade badly. Beds get stained with blood in hospitals, but you don't see doctors and nurses kicking the beds just because they can, or because there are many beds there. Every bed counts. Every deck counts. It should get worn because it's being used and enjoyed, not because it's usually left around to get damaged.