Just look at it from the simple economics.
The economic system relies on most of the adult population working in order to generate money through taxes for all the things that are provided from the public purse - education, health service, supporting people on benefits etc
Already there is a backlash against people who could work but are on benefits (disclaimer: not criticising anyone who can't work).
Can you imagine the chaos if it was suddenly decided that out of that same pot of money, we'd pay parents who want to stay home? Because you can bet your life that there'd suddenly be a population explosion - and it wouldn't just be among families who nurture their children, feed and clothe them adequately, read to them etc - it would be among feckless parents who would realise what a damn good thing they're on to - getting paid a wage to keep producing babies! Not even just benefits, but a respectable wage!!
And what about all the WOHM who currently provide invaluable roles as doctors, nurses, lawyers, teachers etc - what happens when they decide to stop working because actually there isn't quite the same incentive now that they'll be paid a wage anyway for ,erm, being a parent? After all, although being at home with young children does involve work - cooking, feeding, changing, playing - there are none of the pressures that go with actually having a job. No targets to meet, no performance management, no one to sack you if you don't get the kids up and dressed by 8 am. If I have an 'off day' at work, I'm still accountable, I'll get pulled up if I perform at a substandard level. When I was home on Maternity leave with my 3 pre-schoolers, if I had an off day, we'd snuggle on the sofa in pjs and I'd feed the kids a sandwich rather than cook. No one judged me for that - least of all my kids!
There is just no comparison between in paid employment and parenting - NOT because being a parent is easy (far from it at times!) but they are just not comparable things. People become parents because they want to. They have the number of children they choose. I adore being a parent, but its a labour of love - I wouldn't expect anyone else to pay me for what I would do anyway without a wage.
On a final note - I'd love to hear where this wage would come from anyway!!!