The problem is hospitals, insurance, EMRs, and lawmakers continue to lobby for increased administrative burdens on physicians, to the point where more doctors are employees rather than independent professionals. It is a lot quicker to earn a physician income from Day 1 by taking an employed job, than to build a practice. For most doctors, building a practice will leave them financially behind compared to employed peers. A minority of independent psychiatrists will out earn employed ones in the long run, but the main benefit of independent practice is career satisfaction.
Making NPs independent will likely discourage them from starting their own clinics, due to malpractice premiums/lawsuits. But the end result of making NPs independent is employers will still require employed doctors to soak up NP liability, like this: