I basically always leave shoes on, but I try to remember to look and see if my host is wearing shoes - and if they're not, I ask if it's a shoes-off house.

But I grew up in a shoes on house, as did DH, so we have to think about it intentionally.

And I'm never offended if people don't think to ask us!

But I don't like it when people walk with shoes on over DS's play mat, or rest shoes on our counch, coffee table, etc.