It depends on the site but when I was a SAHD, I found many of those parenting sites were not welcoming to dads, even dads doing the exact same work as the moms. Moms there wanted a place to vent about their husbands and men who were pulling their fair share or were handling most of the parent duties simply weren't allowed.
This, it's well known that women want to vent and men want to fix the issue. This difference in communication and perspective has been supported in various research.
It seems like a safe guess that very few of the moms complaining about their partners on r/parenting are also married to the dads who are posting on r/daddit.
It's like how /r/steak is just dudes posting steak pictures, and there is some new cooking sub where it's just women posting food pictures and complaining about their significant others. Women be complaining.
