I actually have an MD, and used to practice medicine in the last century, having given up the vocation for other things in the late 90's. It's been at least 20 years since I used the prefix Dr., or the suffix M.D. People who make assumptions about prefixes and suffixes generally assume that M.D.s are self-important jerks who know nothing about finances or business, so it would be an actual detriment were I to use it these days . . . .

I similarly have no desire to be sought out on an airplane in case of a passenger medical emergency. My medical knowledge was never in that area (emergency medicine), and at this point is so out of date that "Dr. Mushroom" would actually be appropriate :-)