I had a child with my woman,loved her. But that doesnt mean you dont want to still leave it open to having your cake,while possibly eating to too if something comes up.
Plus some of us respect vows so much,and love our women so much, That we dont want to get married knowing we are likely to fail her
The belief is it would hurt her more,and probably be more embarrassing/insulting if I cheat on her as my wife. Cheating while boyfriend and girlfriend is less egregious. This may sound like a silly way of thinking. But this genuinely was my thought proccess. And I still believe its very valid and cant be dismissed.
When you marry a woman you are essentially giving her closure and finality. Which is why its more devestating when you betray her/him in that state. A woman can feel that closure without you marrying her based on your words/actions/commitment level also. But marriage is you cosigning there feeling of security definitively.
Its best to leave your woman with doubt if you are unsure you can do right by her for the long haul. When you are sure,leave your woman with zero doubts based on your actions matching your words. You dont need a certificate,but for many thats their "proof". You can grant her the proof,or keep working until your word is enough. If your word isnt enough,theres probably a reason