Here is the clinical focus data for NP's provided by the AANP.
AANP - NP Fact Sheet
Over 80% of NP's have a degree with a focus on primary care, and as you can see, a large percentage of NP's work in primary care (much more than physicians and PA's).
When I last checked, only about 10% of all new physicians and PA's were going into primary care. This is a nice chart showing the breakdown of what all physicians are doing now.
Only 14% work in family/general practice, and another 16% work in internal medicine. It's entirely possible for physician's in both specialties to work only in acute care.
This article below talks about how a primary care shortage of physicians by 2025 is a very real threat, and one of the limiting factors is the 5-10 years it takes to train physicians, and many of them don't want to then go into a field with slim margins and long hours. What providers take less time to train and still performs competently in primary care?
Significant Primary Care, Overall Physician Shortage Predicted by 225
This article shows how only 2% of medical students consider primary care.
I could go on and on and on. The reality is the medical lobby wants to protect their financial interests, but they have this problem where no new physician wants to practice in the field themselves. It isn't worth it for them to take out between $250,000-500,000 in tuition and loans over 8 years of undergrad and medical school to land a job that will pay them less than what CRNA's are making.
I would be interested to see some data on where NP's are working in states with independent practice versus states with collaborative agreements. I would imagine when your state requires you to be tethered to a physician, and the majority of physicians work in specialties, it makes sense that more APRN's in those states work in specialties as well. It's hard to blame NP's in these states for "choosing" specialties when there isn't much of a choice to begin with.