The SAHM argument is stupid as fuck. SAHM’s contribute to the household by raising the children, saving money on childcare, presumably doing the lions share of the housework blah blah blah. There are other ways people contribute besides cash.
I personally never suggested that SAHMs don't make an invaluable contribution to the household and family. Of course they do - it's a complete partnership. I was just going on the rigid 'My money pays for it, so only my opinion matters' pov that we were seeing in this thread. No relationship, no love, no blood-ties, no trust, no respect - just 'my money: I'm boss'.
You can’t use the “adult” line if you’re not prepared to do anything that actually involves being an adult. For all intents and purposes, and 18yo living at home, completely financially dependent on parents is a child.
And that's exactly the way it will stay forever if no attempt is made to help your son/daughter to transition into the adult world as and when circumstances allow; indeed, if you make a deliberate effort to keep them subjugated as a child and deny them any natural independence when you so easily could.
It's the belief that, because they aren't yet financially independent, they don't deserve any independence, however easily achievable, at all. You wouldn't dream of doing that at any other age or stage:
"No, I am NOT going to hold your arms up and guide and support you whilst you take your very first steps - until you can walk properly on your own, you are still a helpless baby and I don't want to know until you can walk confidently on your own like a proper toddler."