someone questioned whether the UK really is so unusual in keeping shoes on indoors & the answer is yes.
having lived/stayed with families in various countries, I can ONLY think of the UK as being a 'shoes on' kind of place, and in fact a good % of people in the UK do take shoes off.
For some reason, in the UK people worry about showing their socks. In just about every other country I have any experience of, wearing your shoes inside is like sitting down with your coat on & umbrella still held above your head - really odd, you just don't do it!
Loads & loads of countries have houses built with a tile entranceway/boot/mud/laundry room as people arrive at the house, because everyone removes their shoes.
and those saying you value friendship above possessions - that can be turned around. i value my friends sufficiently, that i don't deliberately walk across their floors with outdoor shoes, knowingly damaging them. I would not do that any more than I'd walk past their car, scratching it with a metal clip on my handbag. Nor do I swing on their chairs, causing them damage. It's polite to show respect for other people & their belongings.
oh, and if you're so attached to the look of your shoes, btw, i have received many compliments on a pair of red suede heels, which people notice as they arrive/leave.