Tangent. Back to the car in a moment.
Doctor - from Latin Docere meaning "to teach". Thus, it is a classical title for a "teacher". Traditionally, there are four classic schools. Law, Medicine, Divinity, and everything else called "Philosophy". Philosophy includes everything from engineering to chemistry - physics to literature. The whole process is very much a medieval quirk and that is why I get to dress up like a Harry Potter character every so often. We even get our own "school" colors. Law is Royal Purple, Medicine is Vivid/Kelly Green, Divinity is Blood Red, and Philosophy is Dark Blue. Those four schools have expanded since 1100s to include education, dentistry etc. However, early on in the US, most colleges avoided European traditions and only really offered an undergraduate degree, maybe a post-graduate semi-masters equivalent. It was not until after the civil war when a Ph.D. was offered in the US and it was not until the 1910 that it became an established route. In contrast, law avoided excessive schooling for a very long time (in an attempt to be more "common man" friendly) and you can still apprentice in some states today to become a lawyer. Law still maintains that tradition as lawyers use the term "Mr/Mrs" rather than the title that other nations might use with a JD degree. Thus, the only professional "Doctorate" degree that existed in the US was a medical degree for 250-300 years. So, in common vernacular, "Doctor" is substituted for the term "physician", kinda like Kleenex or Chapstick is used for a facial tissue or lip balm. It is the most common, term that individuals interact with but the term "Doctor" is a title for educational achievement in association with "teaching" or "professing" role. After the whole process... aka 11 years straight through with undergrad, a professional masters, the PhD...and a post-doc, I want to do something a bit more practical/hands on... I was burnt out with the full-time professor process. Plus the wife wanted out of DC where I was so I had to find something else to do. I am a doctor as I teach on the side but I am not a physician since I do not practice medicine.