Um, you can beat the game without killing a single person.
I can make a game like that too. It's called "watching paint dry". You ever played Goat Simulator? Stupid stuff like this doesn't make it a good game. If the story requires literally 0 characters, then the story might as well have no characters. Somebody might be able to make it work, but most of the time it probably just sucks. Wouldn't expect much out of a story that starts with an amnesiac character, however.
Since you somehow misinterpreted it, "Why do you have to kill everybody" wasn't a question geared toward NV, it was geared towards you.
I already did all this "look for your family" bullstuff in Fallout 3. It's the exact same story all over again in 4.
I'm not sure what this has to do with the post you quoted, but whatever. You've posted the 1 = son 0 = dad thing like 3 times now. You're not a genius for figuring this out. Fallout's 3 story made no sense, I'll give you that, but at the same time it was so vastly different from Fallout 4's story line they're hard to compare. In one your father leaves the vault you grew up in to save the world. In the other your son is kidnapped and your wife is shot after you're cryogenically frozen. Not gonna spoil anything, but the outcomes are also incredibly different. I feel like you're just simplifying it on purpose to make it easier to bitch about.