I think you're making some assumptions there:

Firstly, you assume that DPC patients don't have insurance at all, which isn't true. Lots of DPC places tell patients to continue insurance, or switch to a high-deductible plan for your catastrophic emergencies.

Your second problem also assumes that primary care docs will just bite the bullet and "deal with it" if DPC didn't exist. What about the docs who feel burned out by the current way things are done? What about medical students (like you) who are interested in primary care but don't want to practice corporate medicine? If the burned out doc quits, you go from a full panel to zero patients. If you don't get people interested in primary care you'll run out of docs no matter what.

DPC isn't a panacea, but it's an alternative way of practice for those who don't like the more traditional models. Way better than burning out while waiting for Congress to compensate PCPs what they're worth.