>The only reason my chair manufacturer would be entitled to the proceeds of my success whilst I was in their chair is if I hadn't already paid them for the work they put into making the chair for me

Unless you could lease a chair and limit your cost to some finite number (which is higher then upfront cost), because chairs are easy to get by. You could also buy very cheap chairs from China for example and rent them by the hour (or that's what I heard).

The actual reason to why is -- because they can make you do it.

>What other things work like that outside of the modern tech world?

taxes