Yes it is an anachronism and hopefully will be disbanded in due course.
But with regard to Catherine every woman (or man) can choose to be a stay at home mum/dad and shouldn't be criticised for that. She does a lot of visits which aren't recorded.
She's not a stay at home mum though! We are paying for her to work and what both William and Kate do is minimal, and interspersed with a lot of holidays. They both use the ' stay at home parent' excuse for this, but they have two school aged children, a nanny and numerous other staff. What's the nanny doing if she's a stay at home mum? The most annoying thing is that she is put up as the perfect woman ( particularly this week) when she has married someone, had some kids and wears clothes. I doubt she does that many unrecorded visits. The Cambridges work numbers are so low, you can bet they would record everything they do!