Other than ruining their life (or making it highly probable to do so).
During the important nurturing years, Mom is working and the kid is warehoused (with Gramma if lucky, with strangers if not). The probability of a kid going to jail is massively higher for those from a single parent home.
And lets not start about the number of parental figures that will probably stomp through the kid's life, and the kid gets attached, then abandoned, attached, then abandoned, until he/she thinks he/she is of no worth.
It is a choice, but it is a selfish one. MMEEE MEEEE MEEEE! Who cares about the child's welfare, this is ALLL ABOOUT MEEEE!
Oh, and please don't hand me that crap about how someone you know did just fine -- some do, most don't.
No I grew up in a household where the father was in the home and because of social stigma the mother stayed and DV was rampant and it still came out wrong.