Not sure if I'm particularly bothered by this because it's mainly the in-laws who do it, but most people know I expect shoes off as you walk through the front door.
I've mentioned it to dh a few times, I think he thinks I'm just picking at his parents behaviour, but it makes my blood boil... I clean and hoover my home, invite you round and you tread your dirty shoes all over the floor which me and my kids sit and play on (and my little girl crawls around on)
. My parents have the decency to bring their slippers!