I don't think there is any reason why they can't, they certainly have the money for it, they simply don't want to.
There will always be a steady supply of people willing to work in shitty conditions because either the employer is a big name (Google) or they have no other alternative to put food on the table.
The latter aspect is why government regulation and minimum standards are the only way to prevent exploitation.
I mean janitors, cafeteria and cleaners used to be in-house. Maybe managers are afraid of being demoted to manage the cafeteria?