We might not like to admit it, but people can and do, all the time. There's an ideal as far as being a parent goes that we try to hold people to and enforce culturally - but that doesn't stop people from getting divorces or dumping their kids on their partner or parents while they go off and do their own thing. I know a number of people that more or less raised themselves - their parents provided necessities and that was about it.
There's also a larger discussion to be had on parenting and why it takes more time and effort than past generations; the difficulty of raising kids with two working parents; the move away from extended family groups and close neighbors that can help with kids; the increase in helicoptering/worrying and loss of independence; all of which contributes to making things more difficult.
> Just because something "always has been" doesn't mean it's easy.
I never said it was easy. What I said was it's not the hardest job, it's a common human experience, and it deserves celebrating even if it is an average, common thing.