Eventually they evolved into what we now know as "intellectual property law" in the 18th century and that system was all about disclosure. It had nothing to do with "encouraging innovation". What's most interesting is that even back then patents were being abused and hindering innovation. See the info in that Wikipedia article about Boulton & Watt preventing improvements to the steam engine.
The simple truth is that patents are not required for innovation and they were never intended to protect individual inventors; they were designed to protect business interests. To allow established players to keep the up-and-comings out of their markets.