"Hiring" a babysitter means you have engaged her/him for a specific period and compensation commitment. Otherwise, you're just adding them to your Contacts.
Instacart hasn't hired these people in any traditional sense, they've just added those people to their Contacts with no compensation commitment.
That is your definition of hire but it is not what the actual definition of the word is or implies. You can hire a babysitter, 1099 contractor, W2 employee, day laborer, and so on and so forth.
