Billy Wilder (53 years old when SOME LIKE IT HOT was filmed) was originaly from Germany and firmly believed in the "old school" filmaking.
He was a little suspicious of Technicolor (although widely used at that time) because he thought it would simply INTERFERE with the comic aspects of the film and B&W would make the situations seem funnier and more true-to-life. (Plus, B&W was what he was used to shooting in--and his career began in 1929).
A year later, he directed ANOTHER Classic Comedy (THE APARTMENT--also with Jack Lemmon) in B&W as well.
"I say YOU'RE the CUTEST one. No, I say YOU'RE the CUTEST One. And we go on like that from dawn to three."