My mum did. She left me and my sister with my dad for her affair partner.
Even after she left, she never really instigated a proper relationship with us. Luckily my dad was an amazing parent, so I feel that I'm not as affected as I could've been. My sister however has had no end of mental health problems due to the abandonment.
I try not to judge my mother - she had a complex issue with her own mum (my nan who I'm NC), and I even have the odd day where I dream of running away, but I could never leave my children, or not be interested in their lives.
It never leaves you though, even after lots of therapy and understanding. 35 years later I mourn having a 'proper' mum who is there for me.
I have tried to break the cycle though, and hopefully my children will agree with that.
My step daughters mum has pretty much abandoned her as well. Ironically, she said the same thing that my mum said when she left - "what will people think of me?" More concerned about their image than the damage they have inflicted on their children.
A friend's step daughter also lives with her full time, so it does happen a lot more than people think.