I think that's a great question, but I don't think I have a great answer.
My best guess is (1) that there is something romantic about the WWII time period, in terms of the scope of the war and what is at stake and in the technology involved--pretty much every tool of warfare we have today but just barely evolved out of their infancy. And (2), the reduced lethality of ASuW and ASW weapons compared to modern times makes WWII submarine combat much more tense for a longer time. For example, escaping a depth charge attack can provide a really tense experience that translates very well into a cinematic presentation. In modern ASW, the torpedo gets dropped on your head and that's pretty much the end; the crucial time isn't during the heart-stopping action but in the minutes before when you're trying to evade detection. That's more cerebral and doesn't translate as well into a cinematic experience.
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