that is because you are a parent with loads of common sense!
Well, I dunno about THAT.
What I DO know is that with my first child,
I phased myself in. I sent her to the nursery while still in the hospital so that I could sleep. When I didn't know how to comfort her, I called in a nurse. When I was having issues breastfeeding, I asked for help. My mom stayed with me for the first 2 weeks after we came home from the hospital, and she was there every time I needed help.
Why would we deny the same for fathers by just dumping a newborn child on them? Sometimes it's not about keeping the child away from the father, it's about making sure the father is comfortable and capable before saddling him with unfamiliar responsibilities.
My own husband wasn't comfortable keeping the children for more than a few hours until they were mobile... and most of the time wanted me to do my errand running and stuff while they napped so he didn't have to 'deal'. He felt out of his depth with them, and it wasn't fair to HIM to leave the children with him for periods of time for more than a few hours.
My BF has been in my son's life for a year of his 19 months, and HE doesn't want to keep him alone for longer than an hour or two. In a perfect world, it would be different, but the REALITY is that MOST men aren't comfortable with infants for long periods of time.