Don't forget "doctor" Martin King Jr. who plagiarized some crap to get the fake degree while he read scripts written by lawyers from Brooklyn!
Yes, we use titles to show respect.
Human beings are very frail beings, and respect makes them feel good.
Napoleon, I believe, said something to the effect that soldiers would do anything in return for some recognition, maybe like a ribbon, etc.
We refer to "
Dr. King" in order to show respect. If we did not use that title, some people would be very hurt. I remember some Americans of a certain ethnicity felt very hurt when TV newsreaders or ordinary people referred to "Obama" instead of "
President Obama."
So let's refer to "
Dr. Biden," if that makes her (and her family) happy.
(I once read that in Germany -- at least in the past -- if you earned
two doctorates in any field, you would expect to be addressed as, for example, "
Dr. Dr. Merkel."