I have an aunt (a widow of a certain age) who insists on being called "Mrs. John Southend". When her newest daughter-in-law addressed the Xmas card to "Mrs. Mary Southend" she let it be known that she was insulted!
Yes, I was going to say, women of earlier generations very much saw it as honorary to be referred to as Mrs. Their Husband. Which strikes me as so sad -- such a blatant admission that their own accomplishments aren't supposed to count for anything, that their entire status and sense of self-worth had to come from their mates.
(Here I'm talking about where even the husband's first name has to be involved -- not just his last name.)
I see it as more of a sense of unity...as being part of a group. There is something intangible about names but to me a family with everyone having last names seems disjointed...like a patchwork quilt...nothing wrong with it but just a feeling that the union isnt as strong.
I agree that it lends a sense of group unity, which seems like the one good reason to take a husband's name. It's like having everyone on a sports team wear the same uniform. But of course, it's not essential -- families with an assortment of last names can be every bit as strong as the strongest one-named family, and stronger than many.
Here's an interesting thing in regard to names. I once was talking to a family therapist who said that when she hears of families in which all of the children have the same first initial -- for example, Justin, Juliet, Joshua, Jennifer, etc. -- it can be a red flag hinting of child abuse!
I wondered why that would be, and she explained that it suggests a parental attitude of excessive ownership, of enclosure and lack of boundaries.
Of course, this is a vast generalization, too. Don't go calling the child-protection service on your next-door neighbors just because their kids all have the same first initial!