I think many people base their own value within themselves based upon how much their partner needs them. Also for some people, there's comfort in being needed by their partner. "If my partner needs me, then they are less likely to leave me" For people that feel security in that way, it would make total sense to constantly test those needs because that is the only way they can be sure of the future of the relationship.
However, a partner staying with me because the need me seems like a bum deal to me. I would prefer that my partner stay with me because they *want* to stay with me. If they needed to stay, it would infect all the feelings between us and it would no longer be about love, but about security. And as soon as my security is wrapped up in how someone else feels about me, well...that's a whole lotta ugly I don't ever care to experience again.