comment: PhD = philosophiae doctor (the doctor is in the title) 
  A medical degree isn't automatically a Dr. Many do write some piss easy compilation of data, which isn't more work than a bachelor or master thesis. In the old days every medical practitioner also wrote a dissertation and got the degree. That stuck in the mind of most people. In German there is a difference between a "Doktor" and a "Arzt". The latter being everyone who completed medical studies at a university and could also write a dissertation to become a doctor.