Unmarried men occasionally get the title 'Master' although I've only come across that in more formal situations.

I also never said we should or shouldn't use the terms. I don't have an opinion on that and it's not a debate or argument I'm going to waste my time on. I was simply explaining how they are conventionally used. This kind of thing was taught in schools as recently as 20 years ago as part of explanations on how to write and format letters.