I don't keep any of my defensive guns around the house with a chambered round in them. I have nosy and curious grandkids and eventually one of them will come across one of my tactically placed weapons. It only takes a second, maybe a half-second, to chamber a round. My dogs will provide me more than that luxury of time. Safety first.
In the movies, often you'll see a character chamber a round when they already had one chambered...technically. In a John Wayne movie I watched recently, the one with Robert Mitchum and James Cahn, JW had been shooting his lever-action Winchester, stopped to talk, then before going back into action he cocked the lever again. That would have meant he ejected a live round onto the ground...dumb. But, it is only a movie...