The term itself comes from the Latin 'docere' - to teach - and goes back to before the first European universities. The title of Doctor for physicians and surgeons is much more recent, and was actually a status-elevating maneuver. Even today, in the UK and countries that follow that system, a surgeon is called 'Mister' and a physician, who is called 'Doctor', will have an Bachelor of Medicine (MB) degree. The MD in that system is a proper medical research doctorate.
So this notion that an academician isn't a proper or 'real' doctor is quite bizarre and ahistorical, It's also unnecessary to reserve the word to distinguish those in the medical fields, since they already have a number of words that refer exclusively to them, physician, surgeon, etc.