Historically, this could be the underlying reason for the existence of various professions: adjutant, batman, valet, secretary, personal assitant - perhaps the main function they provided was just providing a presence?
Perhaps a function but I don’t think I would go so far as to say primary. They also lugged their stuff around and handled all of the boring parts of life, like opening doors, writing letters and so on, that they didn’t want to deal with.
I.e. all the things technology is outsourcing back to us.