I'd like to offer my threepence worth with a scenario about why motherhood is devalued:
Woman goes to a job interview. The pleasant interviewer sets the scene of what this job entails:
"Now, I must tell you this job is for life. There's no probation period, no leaving, not much holiday and no final salary pension or any pension to speak of at the end. Oh, and I should add - there's no salary. But don't worry, you'll love it.
"The first nine months does entail some changes - notably extreme weight gain, aches and pains, occasionally a spell in hospital - all entirely normal.
"At about nine months there'll be an extremely painful event, which doesn't last long I promise. There is a possibly of death, but that hardly even happens so don't dwell on that. After nine months, the job starts proper and you'll be working with a colleague who can't speak or go to the toilet by themselves. There's no clocking off at six o clock, I'm afraid. You'll need to be on call all the time because this is a very responsible job. Extreme fatigue will become normal after a while, you'll see.
"Now, you may find that other colleagues and partners in the firm go off you big time when you're fully ensconced in the job. That means you're probably doing a very good job. If they happen to leave (which is in their contract but not yours), you'll need to handle everything. You'll be a complete asset!
"Your new colleague will go through enormous changes, as will you, but theirs will include being able to go to the toilet on their own. That's a huge benefit of this job. I can't guarantee that your colleague will support you or even like you - that's not in their contract. When you get very tired from this job, and you will, your colleague may take a contract somewhere else and never come back.
"Don't worry, because you may get some more new colleagues who can't speak or go to the toilet by themselves much later down the line. This is in your contract so this job will continue up until when you're almost dead.
"Er, that will do for starters. I've missed a whole lot out, but we work this job just one day at a time and never reveal the full extent of it, otherwise no-one would agree to do it. Did I say there was no salary? Any questions?"
Woman: "No questions. I don't want the job."
Interviewer: "Oh dear, and you seemed such a good candidate. Now if it helps, I can offer you this hormone in tablet form, which will make you really want the job. Wouldn't that be wonderful!"
Woman: "Sorry. I really don't want this job. I'm off now to have a life. Goodbye."
Sadly, IMO the value of good parenting is beyond measure. If you could pay a SAHM/SAHP roughly 60-80K for the job per annum that may increase the value of the role because of our Capitalist society.
Like the woman above, I could never take the job and I lacked any kind of hormone that would convince me it was a good idea. No regrets.