I think this is mostly a pompous gesture, and don't care for it, esp. for my one friends spot, which, despite being a really nice townhouse, most closely resembles a dope house now, dog, trash, filthy black stained carpets, which is LEASED anyway. If I'm invited to someones really nice, well maintained condo/house, to watch a boxing match, or whatever, I'm cool taking my shoes off, I'll wear loafers or drivers, but all this 'take off your shoes' to sit in the house for 30 minutes is ricudulus. Taking off sneakers, lacing them up is a hassle.
This friends house is a filthy joke, I hate even going over there. Last few times, they haven't tried to enforce the policy, but it's still disgusting.