I have a whole set of "party socks" for mid-winter New England parties
We had 2 dogs and beat up old wood floors so we always told people they were better off leaving their shoes on. I automatically assume that when I go to someone's house in the winter they will want me to take my shoes off what with all the grit and grime on the streets and sidewalks- hence the party socks
So to sum up: summer and fall- I ask first. Usually the shoes stay on. Winter and Mud (that's Maine for spring)- shoes automatically come off.