I can't reference any particular books, but I remember a while back a number of well known directors, including Kubrick, Spielberg, and a few lesser known, discussing their choice of frame size for particular films.
16x9 I believe most closely simulates the human eyes; 2.39/2.4:1 is often chosen whether via by anamorphic lenses, or via simply matting, when the director feels the wider aspect fits the theme, story, landscape, or simply preference for how he visually want's to create his film. 2.4:1 allows for greater flexibility in framing simply because it's a wider workspace.
Kubrick did many of his films in Academy ratio, basically 1.33:1 or what many call square. It worked too, I can't imagine Eyes Wide Shut, which was a very recent film, with major actors, shot in anything but Academy. But few these day's are. I don't think you could even crop down this film, in terms of fitting it for 16x9 without really throwing off the overall composition of each and every shot.
Lastly, many films, even when shot digitally, are shot and captured in a ratio which is larger than the final format. This allows final adjustments to be made in Post Production to either vertical or horizontal framing; or both.
Most of today's content is purposed for 16x9 or 1.85:1 Why? It fits. It's the new standard, 99% of TVs on the market and all theaters are able to handle it.
Big budget films, action, music videos, epics, are often shot in 2.4:1 because it looks simply bigger. It's a bigger shot. Wider, more grand. It feels that way. Take any 2.4 widescreen film; and if you can, zoom in so it fills a 16x9, and ask does it look smaller.