It's not so much about MORE responsibilities, but about the type of responsibilities you suggested. Immunization is okay, but prescribing medications?? That's way too much...
One of the reasons why the pharmacy profession was created was to separate the dispensing/consulting drugs duties from the prescribing duties. MDs, DOs, NPs, PAs, etc would give a diagnosis and prescribe medication(s). Pharmacists would check their work and make sure the patients don't get overdosed or underdosed.
What you're asking is for Pharmacists to give a diagnosis, prescribe medications, and check their own work? To me, that really defeats the purpose of separating the dispensing and prescribing duties in the first place.
(Although, I heard there are pharmacists who do prescribe only under the supervision of MDs.)