You've hit the nail on the head.Originally Posted by Marc Chevalier
I think in many cases, particularly with In Harm's Way, there was a really attempt to "contemporize" World War Two for a "modern" audience. I read an interview with the costume designer of that film and completely intentional on the part of the filmmakers to update the look of the film so that it wouldn't feel old fashioned to the audience.
There was a similar attempt by the makers of L.A. Confidential to avoid things that looked old fashioned, hence the lack of hats in the movie.