I have a cousin that is like this. She's speedrun 3 marriages by her early 40's, and that's not even counting the live in boyfriends that each lasted for a couple of years and then ended disastrously. She is utterly terrified of being alone and will hook up with anything that gives her the time of day because of it. Then it inevitably ends in disaster and she repeats the same mistakes all over again.
This is so alien to me, but I'm maybe the opposite end of the spectrum where I'm perhaps too comfortable being alone. For most of my life it hasn't exactly been by choice (I am most certainly no catch and of limited social value. Sometimes you just lose the genetic lottery.), but it's such a core part of who I am now that I don't know if I could ever live any other way.