The use of former military rank (Sqn Ldr and above as far as the RAF was concerned) as a title was quite normal in the 1960s. Even the local ironmonger in the little town near where I'd grown up would greet his customers using their rank!
But then came 'The troubles' and we were all actively discouraged from displaying or presenting any association with the armed forces when in public - except for parades etc. We all became 'Mr' and had to skulk into work wearing some civilian coat over our uniforms etc.......and to adopt 'sharkwatch' policies.
So it's hardly surprising that the correct use of former military rank is now quite rare.