Welcome..

I understand where you are coming from and thank you for the honesty, I view my mother doing the exact same thing.. Man after man, marriage after marriage.. I believe financial support and security is a factor here, but so could feelings of not being able to tolerate being on their own, this is very common especially from women in my opinion,
I think it's a deeper fear of not wanting to explore their own feelings, so want a relationship to mask having to.