I'm in the Bay Area. There's a serious shortage of general practitioners because the patient:doctor ratio is so high. Even if their absolute pay is high, the amount they are paid to see me is minuscule. They can make more and have many fewer patients / appointments per day if they switch to a specialty.

On the other hand, specialists are more profitable for the "non-profit" healthcare networks we have around here, so they're easy to get appointments with.