They might not have internet. 7 billion people, you might never find that someone, so instead you hook up with losers, and settle on some jackass just because you think it's better than being alone. Then you die.
Not I! I'm done being with a jerk, and I'm definitely not going to hook up with losers, or settle out of fear. There are plenty of good people out there, with internet.
I can't speak to that, and I honestly can't even really imagine what that's like. But in terms of finding someone else, I think most people believe that there are multiple people that you are compatible with. Not saying that you need to immediately go find someone else, just that if it's desired, it's probably possible. Maybe I'm just too heavily influenced by Sleepless in Seattle since I watched that last week.
Then, after a proper period of mourning...you go and find a new someone. No one should be expected to be alone for the rest of their lives.