You're conflating credentials and meaningless letters before or after names. I'm not talking down credentials, I'm talking down titles.
First, "Dr" does not mean peer reviewed expertise. Most MDs do not publish anything peer reviewed. Many Ph.D's publications are not peer reviewed, and just sit on a dusty shelf forever. It's easy to search J.Stor and find literally millions of articles with 0 reviewer information. I think Dr is supposed to mean someone earned a doctorate degree and wants a fancy title, but that is certainly not a requirement.
Second, no, claiming title to property is not pretentious. But calling yourself "Driver Harvey" because you happen to own a car is pretentious. Giving yourself a title based on what you own is pretty much the definition of pretentious.
Jordan doesn't give himself any titles because of his championships. Have you ever seen Jordan sign his name as "King of Basketball, Michael Jordan, 6x NBA championship, 5x NBA MVP, 14x All-Star"? That would be pretentious. Case and point:
http://www.406northlane.com/wp-content/uploads/2014/07/Return-Of-The-King.jpg
Degrees and credentials are fine, but context is important. I wouldn't talk down someone's credentials printed on their resume, hanging on their wall, or in a biography of a publication. Those are important, verifiable, and give credibility to in a situation. But Ph.D.s who insist on having the state print "Dr" on their drivers license are just being stupid, and likewise people who complain that Dr Dre doesn't have a doctorate degree.