I stand by what I said.
Oh, I have all the answers now? First off, you're making it seem like getting a divorce these days is practically impossible or still a social taboo, both of which are untrue.
To answer your question, here's another. Are you suggesting we should just abolish marriage entirely? Is that it? Then we'll have people running around having children with whomever they damn well please. Better yet, no sense of commitment, no meaning anymore to the concept of a life partner, it'd be just one big free for all. I think you fail to grasp the concept of why marriage is such an important institution to begin with. To answer your question simply: yes, go through the legal mess. To have that kind of regulation would be better than none at all.