Your insurance has a pharmacy benefit manager (PBM) that has a formulary (the list of drugs they cover). Multiple insurers might use the same PBM. New drugs are

Your insurance has a pharmacy benefit manager (PBM) that has a formulary (the list of drugs they cover). Multiple insurers might use the same PBM. New drugs aren't automatically covered, as they haven't necessarily made the calculation that the cost of it justifies using it versus the alternatives. It's intentionally complicated in order to fracture responsibility, avoid paying out claims and extract payment from publicly funded insurers.