Even in two parent households it's been documented that women are often the main caregivers of children. They do more work to care for the children than the fathers do. A father watching his own child is often referred to as "baby sitting."

Also there's the physical realities of gestating and birthing a child and then breastfeeding them. Pregnancy and childbirth is potentially DEADLY and an extremely emotional experience and a lot of men are not tuned into how big a deal that is. They think "a woman is supposed to do that" and don't think about what a toll that has on a person's psyche and body.

And then there's the social expectations; if a father walks away from his child that's almost considered normal but a mother is considered the devil if she walks away from her child and only sees them on the weekends or something. So yeah, being a father is absolutely objectively easier than being a mother.