OP's point though is that in some companies, revealing that you have kids at home unlocks a "go home early and never be contacted outside of work hours" perk wh

OP's point though is that in some companies, revealing that you have kids at home unlocks a "go home early and never be contacted outside of work hours" perk which is unavailable to those who don't have (or want to share that they have) kids. It's a tough balance, because if you don't allow the same perks to your childless employees, they end up being "suckers", working extra hours for no extra benefit. Conversely, if you were to eg pay them more, even for working more hours and being extra contactable outside of regular hours, it could be seen as discrimination.