Kylie, these profiles are created under the Integrators project, which aims to create profiles for family members, especially ancestors, for profiles who have been tagged with the "Needs Profiles Created" category. Posting them for adoption on G2G is part of the Integrators project protocol. Yes, profiles are fine without a profile manager but profile managers who have a relationship with the person and family have more of an interest in improving and expanding the family line in the tree.
Great question; thanks for asking.