I used to be from the romhacking community back in the 2000s and due to usage of Windows, open source/foss wasn't even known to most people. The culture of Windows programmers is way more focused on freeware/binaries.
Still waiting to this day for FuSoYa to release the source code of Lunar Magic.
About a central database of binary parsers, I've been wanting this for ages too. The closest I ever found was augeas, but that's for configuration files.