I know it was 1962, but Bond's and Leiter's choice of clothing to visit a beach bar in Jamaica made them slightly less than incognito...
Presumably they picked up on this and dressed more casually for the Bahamas in Thunderball!
Dr No (novel)- Bond is heading out to meet Quarrel for the scene where Annabel Chung smashes a flashbulb in Quarrel's face. No Leiter in this novel.
"(Bond) dressed in his old dark blue tropical worsted suit, a sleeveless white cotton shirt and a black knitted tie."
It would seem the filmmakers are just following Fleming.
Thunderball (novel) "He (Bond) was wearing a very dark blue single-breasted suit over a cream silk shirt and a black knitted silk tie. He looked cool and clean and his only concession to the tropics appeared to be the black saddle-stitched sandals on his bare feet."
"Bond joined Leiter at a corner table. They both wore white dinner jackets with their dress trousers."
"Bond... put on a dark blue sea-island cotton shirt over his slacks."
It was a thing of that era for men to wear a suit and tie virtually anywhere. Certainly, my father and grandfathers were never seen out of the house without being “properly dressed”. If you look at old movie reels of events like the FA Cup Final everyone wears a suit. I remember in the 1966 FA Cup Final a Everton supporter running onto the pitch dressed in suit and tie and being chased by two policemen, the first he evades by slipping out of his jacket before being taken down by a rugby tackle by the other one - hilarious 😂 - it must be on YouTube somewhere.
Here it is: