Jill Biden calling herself "Doctor" is probably the case in point of how ridiculous it is for many, if not everyone who does it, to refer to themselves as "Dr. _______" when introducing themselves. I think she received equivalent to an online degree, but I'm not sure. Unless you have to do some kind of original, significant, research, that involves a dissertation and defense of that dissertation, I don't think anyone should be called "Dr. ______", and certainly shouldn't refer to themself as such.