Not necessarily. Back in the early 1970s I received a letter from Bangor University, offering me a job. It came from a Professor Fogg and began "Dear Cook". After some initial surprise at the apparently curt phraseology, I realised that this was in fact extremely polite - it made us seem more equal that using "Prof Fogg" and "Mr Cook"
Having in my youth, worked for a retired Royal Naval Officer who took exception to me politely addressing him as 'Mr ***', he 1st INSISTED on me using either 'Sir' or preferably, his " Commander" rank. I swiftly pointed out that even the use of the 'Mr' title was a mark of respect which I felt should be earned rather than demanded. However, having already done my homework, I did (accurately & to his disgust) concede on his rank in full as follows:
Lieutenant Commander *** RN (retired) !!! :-) btw..... For those unaware, it highlighted his biggest regret; that he'd NEVER made the grade to the full rank of Commander. Isn't Karma sweet ?