This is very common in the states. You'll see mailboxes, for instance, that say "The Smith's." I notice it but then move on with my life. What bugs me more is people dropping ending Gs. I've heard there are support groups.
That drives me crazy! I could understand that foreigners who just arrived in the country make this kind of mistakes but not the Smiths!
@Truman, I don’t understand what you mean by „people dropping ending Gs“