it's not cheap at all and the privacy and logistical implications of letting a stranger inside your house is something not everyone wants to deal with. I would rather have a robot.
Why not? A recording from a robot can be potentially viewed by a real human, if the company is not reputable (happened with robotic vacuums). But by default, no humans will view it.
A human house cleaner by definition is a real human looking at your home every time.
One human, with a single set of human eyes and a limited network of associates with few immediate criminals looking to take advantage (although, yes, that does happen).
Versus a small army of roomba's and equivalents mapping out floor plans and tangentially exposing human occupation times with that large data set almost certainly exposed to criminal and surveillance networks that will almost certainly use some of that choicer data to their advantage.
Not to pull on the tinfoil hat, but I would assume most commercially available home cleaning robots will be covered with cameras, mics, and other sensors, and connected to their manufacturer's cloud... I don't pay for housecleaning, but I would vet humans quite differently.
I don't trust a robot with my privacy, but I know Linette isn't building a profile of my shopping habits and Wi-Fi traffic. She is also careful to not let my cats out.