[cpursley]

The thing you have to consider is genetics (parentage). Most don't men don't want to raise a child (and all the effort involved in that) that is not their own (without consent, outside adoption, etc). It's a very reasonable position and the basis for this arrangement appearing in most religions and legal systems.

[whodunnit]

Matrilineal societies are a thing.

https://en.wikipedia.org/wiki/List_of_matrilineal_or_matrilo...

[cpursley]

Their are - but even so, they generally couple up and understand who the father of their children is.