Why no pay? Copyright and patents are a pretty new invention in history. Money isn't. Just look how Hollywood developed in the early years by escaping from this whole copyright thing.
That's why.
We didn't have labor and environmental arbitrage like we do now. One could email IP to someone in China who can mass produce it, with lower quality, lower costs, higher environmental impact and ship it across the Pacific a month later.
300 years ago, if someone stole your windmill design and took it to china, you'd never know.