Satin
Sorry to keep you hanging, was offline most of yesterday 
I'm not honestly sure I can answer your question in a way that will incline you to change your views, but I'll have a stab.
For me (and obv I'm the only person I speak for here), it was as a pp said I think - I simply felt this overwhelmingly strong urge to stay with my baby. I don't know where it came from - partly to do with breastfeeding and partly general mummy hormones, I'm sure - but there was no denying it. And I just had to go with it, or I would have been incredibly unhappy.
There was nothing consciously martyrish or selfish about my behaviour. I know it did appear that way to others sometimes. Like you, some people looked at my behaviour and made a couple of great flying assumptions about the causes of that behaviour. I found that patronising, unsympathetic and very unhelpful. I was desperate to be a good mum and here were people slagging off my best efforts?! Yeah, thanks, I needed that!
I also resented that they were putting themselves at the middle of the situation and making it about THEM, rather than my DS. They wanted to look after him because THEY wanted to look after him. It didn't seem to be about what was best for him. My inward response to that was sod off, grow up and get over it. You're the adult here.
With hindsight, possibly I could have done more to try and counter the feeling a little sooner, and push myself to behave differently. But at the time, I didn't want to, it wasn't causing any problems and it would have caused me a lot of stress to try and change. My wonderful DH Got It completely and we worked things out in a way we were both happy with - he got the time he wanted with DS. So if he, I and DS were all happy, that was enough for me.
You mention women "wanting it all" - wanting help with the baby and then complaining because no one else does things right. I'm sure it's an issue with some people, but not me, so if that suggestion was directed at me then you can, with the greatest of respect, stick it
I listen to DH quite a bit on parenting matters as it happens. He's a wonderful, instinctive father whereas I tend to get myself tied up in knots through over thinking stuff.
Finally, the one up man ship thing - again, I'm sure some people do this, but I don't. Everyone parents in whatever way works best for them and I would never attempt to suggest that the more hours you spend with your offspring, the better mother you are. Each to their own.
Does that make any sense?
Tl;dr - some mothers just don't want to leave their babies. That's simply the way it is for them, they don't think it makes them better than other mums, don't go looking for sinister motives that don't exist.