I was thinking about this more and wondered whey other European countries don't distinguish between married and unmarried women with their title. It seems that in the UK/English speaking world it is also a fairly 'new' thing. Mrs historically didn't mean married - it indicated a woman with some kind of status.
newrepublic.com/article/119432/history-female-titles-mistress-miss-mrs-or-ms
It really is time that the assumed meaning of titles of women changed.