Growing up in Seattle, shoes come off as soon as you're in the front door in my family's house, extended family's houses, and almost all of my friends' houses. It keeps the water and dirt confined to the entry area. My parents even have a piece of furniture right by the front door for our shoes to go in (it's about 3 feet tall, 4 feet wide, with shelves and sliding doors). However, I've only taken shoes off outside if they are covered in mud, snow, or paint.
I think that I would only find it rude to be asked to take off shoes if the floor of the house was unfit to walk on in socks or with bare feet.
Also, I see taking off shoes as not only practical for keeping the house clean, but a sign of feeling comfortable in someone else's home. I don't usually wear shoes around my own house, and being shoeless allows me to curl up on a couch or chair, put my feet up, more comfortably hang out on the floor (especially with small kids), etc. When my shoes are on I feel like I'm getting ready to leave at any moment, with shoes off I can really be present and comfy in my surroundings.
Completely OT but funny: My parents' shoe storage unit is some kind of Asian antique, and has little elephant bone handles to slide the doors. When I found out that these were elephant bone (in middle school) I rebelled by calling the shoe storage unit the "elephant killer". Over time my parents stopped protesting when I used that name for it, and now both of my parents and and my siblings call it the elephant killer. It's common for my mom to ask my dad to mail the letter that's sitting on the elephant killer, or my dad to tell my brother to check the elephant killer for his missing shoes! I still get a kick out of the confused look that guests get when my family talks nonchalantly about the elephant killer!