If parents are parenting equally from the offset, I doubt this will always be the case. I was very sick after giving birth, struggling with breast feeding and being unable to go to hospital because of the covid pandemic. My partner had to take almost all the care-giving responsibility while I recovered. Once he went back to work and I continued care-giving, he missed spending that time with our daughter so set aside extra time to make sure he still had enough contact with her. She’s now 9 months old and he’s still the one putting her to bed at night during the week. At weekends, he would have a full day alone with her. Not because I necessarily needed it, but because he wanted to. Now, 9 months on, she is still just as likely to seek out her papa for comfort as she is me.
There’s a reason parenting involves two parties.