Conversely, some makers do keep control. I don't know how common it is these days, probably not at all in AAA games, but I've been contracted in small-studio-land for some things on an hourly basis where I insisted on keeping the right to reuse and open-source any utilities or nifty shaders or logic I wrote, as long as what I reused wasn't recognizable as part of the paid project. This is how I built my own toolchains and frameworks over 20+ years; I'd get paid to build a CMS or an app from the ground up, and then I'd reuse the framework in subsequent projects, improving and modernizing it each time along the way. In at least one instance I ended up having rights to the source code for a startup that got sold to a major company who did not want any of that out there, but sucks for them... because 80% of that stuff was already adapted from work I'd done for other clients under a similar arrangement.