There's a cost to open-sourcing code. It takes effort. You must write documentation and clean up your code in many ways. It's good to "clean up code" of course but is that the most urgent thing on your task-list?

Who should pay for that effort? The original author? Yes if they think it's worth it and they can afford to spend the time on it.

There's also a risk whenever you publish source-code, someone might sue you for copyright infringement, or patent violation, etc.