You've certainly heard the expression "Curiosity killed the cat."
But do you know the second line of the epigram?
"Satisfaction brought it back."
When you close that bathroom door, you're killing them indirectly by their own curiosity.
When you open it again, they get the satisfaction of seeing that "nothing, nothing, nothing--nothing at all" (apologies to Archibald MacLeish) has happened, at least as far as they're concerned, and that the important work of the kitteh committeh can resume.
That is, they can go back to sleep. 