The idea of leaving a woman, alone, with no support whatsoever, after major surgery or a traumatic birth is bad enough, but expecting her to somehow care for a newborn when she should at least get some rest
you can't compare the exhaustion of the woman who has been through hell and her partner - having him to make her feel safe, let her sleep a bit, and take care of a baby would make a world of difference.
No wonder we have horrendous PND in this country treating mothers this way. Yes, of course, there are Kate Middleton who are on their feet and looking amazing a couple of hours after giving birth - but the ones stuck on a ward for a few nights are not in a fit state to care for a newborn!
So yes, partners should be allowed and we should work towards human conditions for new mothers.