A Facebook friend commented on Robert A. Heinlein’s distinctive writing voice. I have noted this myself, and to me it is one of the pleasures of re-reading Heinlein.
It is a very, very midcentury American voice. To me, it seems strongly influenced by hard-boiled noir movies and screwball comedies. Although it is perhaps more likely that Heinlein was influenced by hardboiled authors rather than movies — maybe not Hammett and Chandler directly, but that school.
In Heinlein’s 24th Century, men drive spaceships and wear kilts, but they also smoke Lucky Strike cigarettes. Cab drivers have stogies sticking out of their mouths, and they call men “Bub” and “Mac.”