One thing no one ever considers when they debate whether to REfinish or not. What is the main reason they were parkerized in the first place?

To PRESERVE them, to PROTECT them. It's why I just about always try to refinish the metal, strip and redo the wood. Except for that 1905 03 that I have, (I don't handle it very much), I strive to preserve and protect (sounds like a sign on a cop car) every instrument I own.