That's actually not true. Insurance companies, such as Kaiser Permanente, see a few years of PrEP during a patients active sexual years favorable to treating HIV for life. I have a few friends that are on Prep and have private insurance and have not had any difficulty acquiring the prescription.
Seems to be readily available under medicaid. But you have to keep you income under $15K or ($10K in non-Obamacare states) to qualify.