Keeping with the spirit of Antitheist’s answer: The lack of a positive will to live does not imply the presence of a positive will to kill oneself - and so the default is to continue the status quo. I think there’s both a kind of inertia and an unarticulated instinctive dread of the unknown which hold us back from embracing death, even when life seems to suck. Death just happens to other living things, although they instinctively avoid it. But we humans are quite distinctive: we actually think about it, it matters to us, bothers us (even if there are those who want to deny that it does or should).
