Because they don't like random people knocking on their doors
The girl necks door.
Hold the door! I'm a leaf on the wind!"
They like to stay anony-moose
Guy: I spy on people. Girl: Really I like to take long walks in the park and go to the movies with my friends. Guy: I know.
Knock on the door
Knock on the hatch.
Mali-BOO
Because he doesn't want to be taken as a conjurer of cheap tricks.
Nobody asks, 'who's there ' when you try and tell a knock knock joke.
Knock, knock, knockin on Heavens door
A Jehovah's Witness.
WITNESS ME!"