Looking around my generation of cousins in our family, there are quite a few of us with educational and/or career accomplishments that entitle us to various honorifics. Several have doctorates in various disciplines: PhD, MD, DDS, EdD, and DPhil (that’s Oxford’s equivalent to PhD). All of them use the honorific “Dr” professionally from time to time, but only the physician and dentist use it socially.
Similarly, neither of the retired colonels among us use “Col” socially.
Although many of us are still working, the youngest is old enough to be drawing Social Security. We’re comfortable with who we are and our accomplishments, so simply being Mr or Mrs is enough.
UPDATE—For the record: In terms of university degrees, I’m the least educated person in my generation of the family.