As RVDT says it’s the old brit class snobbery bullsh!t. The retired Big airlines site uses it all of the time.
When I was a youngster the retired Pongos would be quoted as they were captains which was a commission awarded by the Sovereign and entitled to use it - not a job title.
Some even had it listed in the telephone directory; to me even worse than thinking I would be impressed because they had mastered the handshake.
A sign of self importance.
Mind you my second look see on the VC10 was to Bermuda, the skipper’s previous trip was at the end of the public school term and had a cockpit visit from a sixth former who invited him to dinner with mummy and daddy. After dinner she drove him back to the crew hotel in daddy’s Jaguar and insisted on a visit to his suite (good old days). One thing led to another and whilst he was being a very lucky man she called out F@@k me captain repeatedly…rank has it’s privilege even if it’s a job title.
In hindsight I’ve missed out, have to have some new stationery printed.