Lots of people here just don't get it!
one of the great things about cinema is that a movie exists within its own reality that is separate from the reality in which we live. that cinematic universe can be as similar to, or different from, our universe as the filmmakers want it to be
a movie doesn't need to follow our rules, customs, norms, or best practices to be good. a movie has no call to be believable in the context of human reality here on earth. in order to be believable in cinema, a movie need only establish its universe and remain consistent within the reality it has established
that is the beauty of fiction, and particularly the beauty of fictional cinematic narrative
to all the people complaining that Lars and the Real Girl isn't realistic, I say loosen up, forget about real life, and enjoy the ride, because creating unrealistic worlds for us to visit is one of the greatest things cinema does for us. if you can't appreciate that, stick to documentaries (but not documentaries made by Herzog)
Who cares about stairs? The main thing is ice cream.