I prefer the current system too.
When OH and I got together she didn't have anything, but I had a hefty inheritance from my deceased mother. My inheritance was a big thing for me, emotionally as well as financially, and it also gave me a level of security I'm highly unlikely to get any other way, due to disability issues. So I absolutely would not have wanted to risk losing that to a break up.
But I did love OH and wanted to be with her. As it was, we cohabited for ten years. She lived rent free with me, and I had a stable home, even when I had periods of ill health and couldn't work. Eventually, my health stabilised, our lives improved and we decided to start a family and got married. But I am really glad we could do that when the time was right, when we were ready to merge finances, and make that kind of commitment.
I absolutely didn't feel the same ten years ago. But I am glad we got to live together, and obviously our long term future was also hugely improved by her not having to pay rent for those ten years and build up our financial security in other ways. I would hugely resent being told that, effectively, cohabitation = marriage and there's no other option of being together. If you want that relationship, get married, or buy a house as joint tenants, or something.
If you don't, then don't. But it should be an active decision.