Do you remember a few years back when porn stars Karlie Simon and Jai James were at HOD regularly? I was always amazed that ladies who would probably have no problems building up a fleet of regulars as Independents were at HOD for so many years.
Perhaps it could be reasons of safety or they prefer to have a third party manage their bookings and do not want to go through the admin or hassle of weeding out timewasters, dodgy characters etc. Either way, from the outside it looks bad on her to drop from a top agency listing to a bottom tier one perception wise.