If it's important to you, include it.
It's not going to be important to everyone. In my work emails, I include a pronunciation guide to my name, because that's important to me, I know others who have the 'I'll respond to anything close' mindset. Neither of us is worse, we just have different priorities.
If the dentist didn't give you a way to do so, then yeah I can see the annoyance, but it reads that you just didn't put a title. They're going to have to assume something if no title is used, and we're not yet culturally at a place where going without a title is accepted (particularly by the computer systems they put things into most of the time).
It really is depressing isn't it, that so many women don't see the patriarchy at play in marital honorifics?
While sexism comes into play - though more in the fact whichever title we use, we get a partial word because of how the word mistress that they all come from is treated as sexual - it's stems more strongly from classism. Prior to the late Victorians, it wasn't assumed everyone had a title and the titles for women were more associated with class or profession (hence why women teachers are still mostly Miss). Texts of the time show unmarried women using Ms and Mrs, plenty of married Miss. Moving into the Edwardian period, young women from monied families largely used Miss - that fashion is how Miss became associated with unmarried women when there was a cultural shift that everyone should have a title, that this is how we're respectful, that this is the proper way to be even though it's still seen in many professions who actually gets their title used regularly and who gets called by their first name is still largely around hierarchal classism.
I don't think it's depressing that it's not seen that way, it's one of many lenses that can be used.