My wife took her FMLA (unpaid) leave directly after pregnancy, then I took my (company benefit, paid) 16 weeks after that- with a two week overlap so that I was comfortable with all the work necessary. It meant that the kid spent the first half a year of his life with a parent providing care every moment, which was great, something that I am so grateful for, and something that I wish every parent could have an opportunity to have.

While I agree that the benefits of involved parents are most notable for kids at an older age, I think that the effect on the parent is largest at the beginning. Humans don't demonstrate their love by providing care, they provide care that turns into love. It is in the unrequited acts of service like changing diapers, feeding (bottle or breast), and rocking to sleep that build the parents feelings for the kid.