I could see having this kind of policy for "the good front room" but not for your every day sitting room.
My mum and dad have lived in my childhood home for nearly 30 years, and for as long as I can remember the good front room is out of bounds for entry except for special occasions and the pets are banned. Even on special occasions theres no food allowed, beyond a biscuit or two, and drinking is limited - tea/coffee is fine but definitely no red wine etc. The furnishings in there is almost as old as I am but they are in pristine condition.
The every day sitting room, on the other hand, is a free for all in comparison. Food and drink is allowed, the cat sleeps on the sofa etc and it is a comfortable room that is set up to encourage socialising. We all love coming round and just hanging out with family and friends and my parents house has always been the place extended family gathers for parties etc.
I could not imagine coming round to my parents and not sitting on the sofa with a cuppa, putting the world to rights while the kids play on the floor.
Also, I notice that a lot of people on this thread ascribe spillage to cups being put on the floor ... my mother has a coffee table and side tables everywhere as well as extra nesting tables for if the emergency chairs are brought in, so there is always a table within arms length of anyone who might need to put a drink down so no cup ever ends up on the floor where it can be kicked/knocked over.