Deliberately using a wrong “married” surname - why do you do it?

[mumdom]

Perhaps this ought to be in AIBU but I’m not interested in the usual MN bunfights, I actually want to understand the thought process involved.

I gave a lunch party for a family member’s birthday. The thank you letters have rolled in - not expected as family guests only, but obviously I was delighted to receive them. As usual, my mother-in-law and my sister-in-law have used the married surname I have never used on the envelopes. I’ve been married since 2005, so it’s not news. I’ve told them, politely and on numerous occasions, that I didn’t change my surname on marriage. They still insist on using it.

The usual MN explanation about this behaviour tends to be of the insecure cunt/ generational misunderstanding/ jealousy about professional qualifications or career kind. I’m as certain as I can be that these don’t apply to my MIL or SIL so I’m asking now: if you deliberately change the surname of a married woman, why do you do it? Is it an etiquette thing, or a contempt thing? What are your thought processes? Because choosing to use a different surname to the one a person has been known by for nigh on five decades clearly requires some thought, no?

I take issue with PPs who say it’s just a small thing and doesn’t matter.
If someone asks who you are, how do you reply?
You give your name, don’t you? It’s your core identity, it’s quite literally “who you are”. That’s quite a big deal for close relatives to deliberately get wrong. I’d be tackling them, OP, and asking why they persist when you’ve made it plain it’s not your name and you object to it.

I’ve pondered this in my own case but can only speculate on the individual motives involved. DH and I married ages ago - now over 30 yrs and didn’t change my name. DH is unbothered but I had to train him in what to say. He’d say things like ‘Unholy kept her maiden name’ and I’d be like ‘It’s not a maiden name, it’s just a name, I just have never changed my name’. And I’m no maiden! This sounds like it bothers me a lot, it really doesn’t. In school (we have dc) I’d answer to MrsHisname and MsMyname. I’d never sign my name or fill in his name - it just isn’t my name - but I generally don’t correct people. Not that much anyway.
But relatives! My late MIL took it on board but clearly didn’t really get it. She saw a tv prog about women not changing name on marriage and decided it’s because I’m Scottish. Maybe there was someone Scottish on the prog. Who knows. After a few years she started calling me Mrs his name. I wondered if it was getting older and maybe she forgot. In my family I had an aunt and uncle. My aunt was aghast! She even said to my mum ‘Why’s she even getting married if she won’t change her name?’ Yet if I tried to discuss the issue she’d switch off the conversation. I think she just couldn’t understand. She was a dreadful snob and cared what people thought and this was just too much. Uncle never voiced an opinion in my hearing but I suspect he disagreed with her but couldn’t say so. Letters and cards from them always were addressed ‘Ms Myname’. I think she thought she was being funny. Once they sent a cheque addressed to Mr and Mrs etc. I wrote a very polite note saying thanks, it was a kind idea but there is no bank acc of that name. To her credit she sent another cheque with my name on it. They were v generous. But all this fuss. I think Aunt just couldn’t accept anyone could do things differently from her. Yet when Aunt died my name on her Will was correctly listed as FirstnameSurname. Honestly don’t know - it was maybe just a silly game on her part.

For me, this happens because of assumptions. I'm not aware that anyone does it when I've actively insisted I haven't changed my name.

Almost all of DH's family assume I took his name, and I doubt any of them would know my 'maiden' name. Younger relatives on Facebook would see, but his parent and aunt/uncle generation are completely offline and would have no reason to come across my name.

I haven't told them it's wrong because they don't just address cards as Mrs [hissurname], they address them as Mrs [hisfirstinitial] [hissurname]. (And no, I don't have the same initial as DH.

So not only does my 'maiden' name not matter, but my first name doesn't either. I figure this shows a lot more -sexism- tradition than just assuming I took his name, so I don't have the argument. I have better things to do.

For my part, if I'm writing to a couple, I would never include surnames. I would always use 'Jane and Tom', as anything else feels weird and too formal.

@HillRunner Yes I know that, I was being self-reflective.

I was saying even though I have rejected the taking of a male partner's surname myself, I can detect that I must still have some internalised patriarchy! Also I was trying to suggest insights into the OP's in-laws psychology as she requested.