But then I just don't understand the luxury of being a SAHP as have always had to work & fit household stuff around it. I think adults should be equally financially responsible & that includes earning it
That's because you can't think outside your own situation ocelot7 
In our situation, my DH works long and unpredictable hours. He's often away, he never knows what time he'll be home. He LOVES his job, it's like a job and hobby combined for the satisfaction it brings him and it is extremely well paid.
If we prioritized my return to paid work, we'd be only less money because you can't earn what he does from a more predictable and less demanding job, my earnings wouldn't make up the difference for many years, our DD would need to be in childcare which would further deplete the household disposable income, both of us would have less family and leisure time and somebody else would have more time with our DD to shape her as a human being than we do. It was important to us both that one of us always be at home for her when she wasn't at school. We'd be poorer in all respects, not just disposable income.
Oh and unlike you ocelot7, my DH and I value each other equally and don't accept the values placed on us by employers as representative of value we hold for each other in our relationship. That's why when I was bringing home more than 6 times what he did when he was on his apprentiship, I didn't lord it over him and think that bought me more power in our relationship. Likewise when I was a SAHP/WAHP and my DH's employment fortunes had changed, we continued in that tradition of valuing the virtues of our partners equally and not seeing earnings as any basis on how to divide up power in our relationship 