I am Scottish, in my 50s and didn't go to Uni for some of the contexts that have been mentioned (and very unKardashian 🤣)
I was Miss Breath Miller as a child and then became Ms Breath Miller as an adult regardless of my marital status the same as my Dh was MasterDH as a child and became MrDh as an adult.
Most of my friends (Scottish and 50s regardless of education) are the same. One or two who changed their name and went by Mrs regret it now.
Some of my family seem to find it the hardest thing to get their heads round and after 20 years of marriage I still get cards to Mrs Breath DHname. It annoys me to be honest, I find it disrespectful, they are making a point that they disapprove of my choice. If I correct them there's a bit of eye rolling like I'm being difficult.
When I was around 14/15 my English teacher in the 80s (in Scotland) got married in the holidays. Someone asked her what we should call her now and she explained the term Ms and said she had not changed her name and why. I was most impressed and thought "that's for me when I'm an adult"
I actually feel very strongly about this and whilst respecting what other people wish to call themselves and always do call them by their chosen title and name, I do wish it would go out of expectations. To me there is a sliding scale..
OfDhName (eg Offred), MrsDhFirstNameDHSurname (as my Grandmothers were still called at times), MrsMyFirstNameDhSurname.
I personally find it all archaic. (I also chose not to be "given away" by my dad when I got married)
I have 4 children, 2 while unmarried to my ex partner and two to my now husband. I have a different surname to both pairs and it doesn't bother me.
But, the biggest thing for me is respect for choices. Call yourself what you want and as soon as I know, I will call you that. But, I would default to someone being a Ms unless I knew otherwise. I would not presume a woman was a Mrs because she was either an adult or married.
In truth the only time I use a title is in form filling, when addressing cards I just put their (preferred) name with no title unless they are (generally speaking) older and I know it is important to them.