Do families need a stranger for a role like an aunt for their children?

I can't understand why families may offer a nanny the promise to become an extension to the family.

Excelling nannies have come a long way. They have crafted a title and they invented the relationship that fits the title well.

Working for the family or working with the family 

Nannies know their status surrounding the family environment. There is an invisible level running parallel to those of the parents that is reserved specifically to place one person only: The nanny. It is the level where everything is about the family's children and where only nannies have the potential to turn challenges into wonders like crying to smiles.

Only highly qualified nannies can walk into a house to learn where everything in the house goes, what the family eats, their preferences, their ideological beliefs, the family's boundaries and the family schedules; and with minimal interaction from the parents, that nanny is capable to manage the household as the parents would, proving they didn't have the financial responsibility to keep their family and the house running or just need lots of free time.

The parents' trust in the nanny’s performance when they are away is the mission of the nanny just like keeping the children safe is. She knows her ability to guide and up-lift the children by implementing the family's norms and routines while their parents are not in the house. 

She is committed not only to herself but to the consistent execution of mastery at the workplace on a daily basis.

When parents appreciate a nanny's value, they can’t see her wasting energy in tasks suited to other professionals.

However, to proficiently carry on the mechanisms of the family by keeping a positive environment for the children, building strong connection with them by understanding their emotions and encouraging self-awareness, resilience and their sense of purpose, besides keeping the children in motion, transporting them to activities, teaching them healthy routines and by continually keeping the children busy and entertained etc., the mental state of the nanny must be in a well-being stage at all moments. She needs to be able to manage a stress free environment by being strong mentally and physically herself. She needs to eat well and be well rested by taking enough recharge times throughout the day at work.

Families wanting to employ house cleaners and babysitters should be able to afford them

Other nannies work is limited to specific tasks that require making beds, vacuuming, doing laundry, cooking, feeding the children, washing bottles and dishes, mopping the floors etcetera. They can change diapers, take the children to the park or for walks around the neighborhood. They supervise the children with very minimal intellectual interaction with them. These nannies might put the children to bed at night and leave work after the kitchen is clean. Nanny/housekeeping vacancies are in demand among middle class and low income families. The term nanny/housekeeper completely removes the value of all nannies. In ancient times, only high-ranking people employed this type of servants for the convenience of having less money working for them. From my perspective, undertaking this type of operation should be declined by families and also by the nannies accepting this type of work.

Working for, or, with the family never qualifies a nanny to become a family member, the nanny is there to exchange the deliverance of  her experience, a great attitude and hard work for money