What do you do? You've got four minutes to find shelter. You might be in the street, or down a lane, miles from home. The government knew the score, they had big bunkers. There wasn't a policy to protect the population like that.
A clean and tidy house would help you survive. Think... there wouldn't be any electricity. You don't want to be falling over piles of crap, and you want to find things where they should be, quickly, to avoid exporsure to radiation. Also, if it's clean, you're less likely to get an illness. You're probably on the edge anyway, so anything you can do to improve your lot must surely help?