There are tons of examples of things that are now in the public domain because the inventor didn't realize at the time that it was potentially patentable.

Sadly, there are also things that are patented by someone else despite all evidence of prior art because the law is now first to patent, not first to documenting / executing / whatever.

I was in entertainment and I most certainly copyrighted things that I had written and my lawyer was excellent at this. And I also worked in tech and created several tools to make my job easier, as well as kickstarted an entire industry around an equation that made things computationally simpler (I was doing AI work that required mainframe access during the time of the 486...I got it to work on commodity hardware that actually was faster than the previous code on machine many times the price and increased the accuracy of the model).

And stupidly, and against the advice of my lawyer...I decided to present all this information at a conference hopefully to help others that were working in the same field a I was. Guess what? A commercial vendor that was at the conference implemented it and patented it. The other stuff? When I refused to patent it, my university picked a professor I had minor contact with and allowed him to claim that he was the inventor (because in a professor / student relationship it was assumed the professor was the source of the idea). In both cases, I received no credit...AND I was forced to remove all material I had published because the commercial vendor as well as the university technology transfer unity all claimed I was infringing on their work.

Sooooo...if you have an idea that is worth patenting, FUCKING PATENT IT. If you don't, someone else will.