I don't think anyone has ever asserted copyright on the bible. I'm not quite sure what you're talking about? As for pamphlets, copyright can never prevent you from printing something that you created.
I'll have to brush up on my history of the protestant reformation, but I'm under the impression that for a very long time the church had a monopoly on people with enough dedication and support to sit around copying books by hand. There was no need for copyright law because it was totally legal to kick the rabble rousers out of the monastery for any old reason.
In this way, the church had been asserting copyright on the Bible for hundreds of years. It wasn't until the invention of the printing press that they needed a law for it.
It's easy to find legal text today that says it's for one thing but if you're in the know it's clear that its purpose--the side effect without which it wouldn't exist--is unstated or hidden. I'm skeptical that our picture of the 1700's is good enough to solve the same puzzle that far in retrospect, but my hypothesis is that if it was, we'd find things were a bit less about protecting authors economically than a surface-level read would lead us to believe.
