You mean to make a documentation on the design and how to build it from scratch? There is the Open-source hardware community which is doing stuff like that; https://en.wikipedia.org/wiki/Open-source_hardware

It’s just a lot of work and much more complicated than open-sourcing software source code. That is - I guess - why so few people do it. On top of it there are not many people who would reuse it because for most people it’s cheaper and good enough to get a modern version from a commercial vendor.