I can't speak to what everyone else has experienced. This is just my perspective after my experiences.
There's something to what hayden said regarding survivors guilt. Quite a bit actually. I still experience it from time to time. And probably always will. But there is more.
As mentioned, and like others, I don't like talking about my experiences at war with my family members. I am considerably more open with (some) strangers.
Why? A few reasons:
It's easier to be open with strangers. With people you have no personal connection with, it's, for lack of a better definition, like speaking to a wall or other inanimate object. You know, you KNOW, you won't be judged by a stranger, or even if you are, it's someone you aren't in any way attached to, and therefore that judgment holds no weight. You can say everything about what you went through, and what you felt, and have no filter in doing so. It's like pouring smoke into the wind, knowing that it's going to disperse and be of no further consequence.
It's significantly less frustrating. Family members, by and large, simply don't understand, and can't understand, what we went through in war. And there's no way to adequately describe it. None. That brings on a double-edged frustration: that the family members don't understand, and that you can't describe it in a proper way. With a stranger, you don't really care if they understand or not.
Some of us, or at least me, feel some unknown need to protect my family members from what I experienced. There's nothing pretty about war, especially for those that have been in direct combat (thank God Almighty I never was). Not one goddamn thing. Even the mundane office aspects of it aren't pretty. We want to protect those we love from the ugliness. And we are afraid that even talking about the goofy funny shit will lead into the ugly. Or at least I am.
You won't, by and large receive pity. There's a tendency among family members to blanket us as veterans with an overdose of pity after we relay our stories, or at least I have witnessed this. Especially if we have talked about something traumatic. We, generally speaking, don't want that. Let me say it again: WE DON'T WANT PITY. Sometimes we don't even want empathy. We just want to vent, receive understanding if it's possible, and move on. But no pity. Talking to strangers, I've generally not received pity.
Anyways, that's my view.