Wearing Shoes onto Bed

Why do Westerners wear shoes onto their beds? Even on their sofas and couches; or perching them onto their coffee tables, and such. I've seen this quite often on movies and TV shows (guests sitting leg(s) up with shoes on sofas/couches/armchairs on talk shows). Let alone manners, but they must realize how filthy the bottom of their shoes are, right? We never wear shoes in the house. We always change out to home footwear or just plain socks right at the entrance when we first enter the house. Our shoes and footwear are strategically neatly stacked on their shelves in the closet nearby the main door. Throughout most of the world the bottoms of one's shoes are seen as the ultimate of filth (and rightly, considering where they've been) and by just showing them to another person can be seen as the ultimate insult. Remember President Bush (son) shoe-throwing incident by an Iraqi journalist? And, the irony is hand-sanitizers are ubiquitously populated among us. We're so afraid of germs and bacteria that hand-sanitizers become a norm in our lives, but wearing shoes in the house, onto bed, onto sofas/couches... is also a norm?