Yep, I usually wear shoes easy to slip in and out of .  If I have a seller who is particular about their floors, I supply booties (like what painters wear) in a basket so folks don't have to take their shoes off.

I was showing a new construction where the MLS notes said sternly: TAKE SHOES OFF!!!!!  When I got there, the place had paper runners all over the place anyway - so we DIDN'T take our shoes off.  It's one thing to keep the floors clean but to keep the things clean that are supposed to keep the floors clean, come on...that's a bit much.  LOL 

Rather than refuse to show the house I would ask the buyer if they objected to removing their shoes.  I also have some of those booties in my car that I can give them if they don't want to remove their shoes.

Respect works both ways and it's not unreasonable for a seller to want to keep their floors clean, especially if they have light colored carpets. 

My guess is that if people are that concerned about their floors and they have a dog, they probably do wipe the dog's feet before the dog comes in.  One of the ladies who owned a house I sold did that - she let the dogs in through the garage and made them stay while she wiped off their feet with an old towel before letting them into the house.

I honestly don't have a problem obeying the seller's wishes - those booties are great for times like this.  I got the idea from Jennifer Fivesendal here on Active Rain and ever since I've kept a packet of them in my car for this very purpose.  No need for anyone to be offended or made uncomfortable - our job is to make everything go smooth as silk - or as paper booties.

They're reusable and not too expensive - a pack of 3 pair from Home Depot are about $4.  Imagine how professional your buyers will think you are and if the sellers are there - you'll make a good impression on them too.  And if you have a fussy seller, why  not provide a basket with a half dozen pair of booties for them to leave by the door.  You'll be the supreme agent in their minds!