According to this , it has never been all that common. Going by the decade of first marriage
Pre 1970 - 14%
1970s - 17%
1980s - 14%
1990s - 18%
2000s - 19 %
2010s - 22%
This is definitely the sort of thing that is going to vary by who you know - I literally don’t know any married women who did not change their names other than myself and my daughter. And it’s also going to vary based on how you see a woman who adds her husband’s name, hyphenated or not , or one who legally changes her name but uses her birth name professionally. If you count those as "not changing your name ( I don’t ) it will be higher but it still won’t get to 50%.
I just realized things have changed since the 1980s. Back in the 1980s, yeah, an experienced letter carrier probably has a good idea of what areas of the country certain types of mail come from and could reasonable guess as to the nature of the contents of that little discrete package. But then I didn’t take into account how much mail order business has increased since Amazon, eBay, and other retailers entered the market. Maybe it’s more difficult for a letter carrier to know these days simply because people are getting more thigns delivered.
I recall reading about some scam in the early days of home computers. they were selling something, but offered a refund when they failed to deliver. The catch being, the refund cheque was printed with the name that indicated it was from an extreme gay pron company, so a large number of recipients wouldn’t cash it.