SCOTUS is ready (again) to overturn 90 years of legal precedent to create a new standard.
It boils down to employment law. The Doctrine of At Will Employment. Most of us are employed (usually unawaredly) as At Will employees. IOW, you're hired and you work at the whim of your employer. And with a few exceptions, you can be fired for any reason -- or no reason, arbitrarily.
The other form of employment can usually be found in Contract Employment. Unions generally have contract employment. Public school teachers, for example, have these contracts. If there is a question of misconduct or failing to meet expectations of employment, teachers can't be arbitrarily fired. They are protected by due process, whereby a review of their services are mandated. OTOH, substitute teachers can be dismissed as at will employees, if not independent contractors. This system also keeps teachers from being fired for political reasons or pressure from any parent.
The fact that SCOTUS would likely change the federal agency system makes the whole federal system open to corruption, political, and less effective in service to the American public.