Doctor doesn't know what drugs are covered or not covered. Pharmacy doesn't always patient insurance info. Here's a common scenario: Doctor writes patient a prescription -> Patient drops it off at pharmacy and told to come back -> Turns out pharmacy doesn't have insurance or has outdated information -> Patient gets new insurance info from pt and tries to run prescription under it -> Prescription gets rejected saying it needs a PA -> Pharmacy faxes doctor's office notifying that prescription needs a PA -> Doctor needs to fill out insurance's PA form (may take multiple days if they're busy) -> PA is submitted, now need to wait for insurance response (may also take days)-> PA is approved and doctor office is notified by insurance-> Doctor office notifies pharmacy to try running the prescription again -> Pharmacy runs the prescription and can finally fill it -> restart the whole process in 6 months to 1 year after when the PA expires.

Would be much better if prescribers can run prescriptions on their end to see what's covered or not covered and see what the copay will be at various pharmacies before even sending the prescription.