Because when filmed and viewed in a movie or on television, the screen doors and/or storm windows obscure from vision anything that is on the other side of them. ~
As much as I enjoy watching Alfred Hitchcock's "The Birds," I never noticed this scene's details until I recently read an interview with (my favorite) actress Veronica Cartwright. She plays "Kathy" in this scene, Rod Taylor's ("Mitch") younger sister.
In the interview she talked about, that at the time of filming the movie, she shared her concern with Hitchcock that there was no door they were walking through - he kindly assured her that it would be done with lighting effects. Sure enough - - Rod opens no door. :)
the 0:10 to 0:33 seconds mark in this video (I hope it posts)
[I know I've shared this story once before on the site here - if it was with you, I apologize for repeating it.]
This post was edited by WelbyQuentin at November 28, 2019 9:23 PM MST
In England.....none of our homes rarely need them.....Our old Victorian homes mostly all have Single glazed double hung sliding windows in them and many still have only 3mm thick glass in them .. The 130 year old ones are a real dirty job to change the ropes in.....the dust is really fine from cars rubber tyres and fuel polution particulate emissions ..:(