The op said 70% of the procedures that he performs are cleanings. This means that there are only enough cleaning patients to fill 3.5 days in a 5-day work week (3.5 days/5 days x 100 = 70%). If the owner hired a full time RDH, instead of the OP, a RDH would get to sit around doing nothing 30% of the time and would still get paid a full time salary. And the owner would have to work harder because the hygienist cannot legally perform other dental procedures that only a licensed DDS can. By hiring a licensed DDS like the OP, the owner can dump more procedures (not just cleaning procedures) that he doesn’t want to perform to his associate dentist. Because his associate DDS can do more procedures for him, the owner now has more time to focus on more productive and complex procedures. Being more efficient helps the owner to produce more.....much more than if he hires a RDH.
Another reason for hiring a DDS, instead of RDH, is the owner doesn’t have to follow the labor law since most DDS’s are hired as independent contractors…. their hours and work days can be cut and they can be let go any time.
These are just my guesses.