He never spoke of what he went through, what he saw, what he knew or what he may have heard of. He was my grandmothers brother, my Great-Uncle I knew he was in the South Pacific from ‘43 to ‘46, in the US Navy, was in “communications” of some sort and made it ashore much more so than the average seaman. He was so tight-lipped that even his wife knew nothing of his war experiences. I suppose it was common, and is common, that those who were there and who made it back are not the sort to complain or to blow their own horns.
I have heard of similar responses by Veterans from a variety of theaters and eras. I think that in many cases it's because what they endured was so horrible, bottling it up inside became a self-protection mechanism of sorts, in that it helped to remove the awful memories to the back burner, at least a little bit.
It's also because they're from the pre-Oprah generation, and they know that it's not manly or decent to babble and whimper endlessly about your own problems or bad experiences.