Because dating is work and always changing partners gets old fast. Most people trade freedom for security as they age. I think people just want to find someone who is “good enough” and compatible enough to not make their lives harder. (That doesn’t mean settling btw. Being single is a viable option for many.)

Women generally make their own money now, so “providing” for anyone but yourself is no longer necessary in most cases. People will have to rely on their kindness, character and charisma to get and keep relationships now. Oh, darn!