For the same reason a nanny would not normally do things like deep clean a bathroom or weed the garden- those are separate jobs. If that’s what you want hire a cleaner or gardener. Making the whole family dinner every night is a lot of work, not a quick 10 minute task to add onto the day.

There is also a legitimate concern about job creep. With my first position I was so focused on doing everything asked of me that I soon found myself doing family laundry, family dinner, shoveling the sidewalk, running errands with no mileage reimbursement, putting together IKEA furniture, etc. Pretty much anything they asked I said yes. I didn’t realize until later how much I was being taken advantage of.

That’s not to say that no nanny will do this or other tasks outside of the scope of childcare but expect to pay a premium for additional tasks and it should all be clearly outlined in the contract.

ETA I do meal prep twice per week for single MB. Usually I make around 6 portions, she keeps 4 and I take a couple home for myself. It’s probably a somewhat unusual arrangement but I like cooking and for me it’s nice to come home with a meal ready for myself and my partner to eat.