Context:
Permissive licenses (commonly referred to as "cuck licenses") like the MIT license allow others to modify your software and release it under an unfree license. Copyleft licenses (like the Gnu General Public License) mandate that all derivative works remain free.
Andrew Tanenbaum developed MINIX, a modular operating system kernel. Intel went ahead and used it to build Management Engine, arguably one of the most widespread and invasive pieces of malware in the world, without even as much as telling him. There's nothing Tanenbaum could do, since the MIT license allows this.
Erik Andersen is one of the developers of Busybox, a minimal implementation of that's suited for embedded systems. Many companies tried to steal his code and distribute it with their unfree products, but since it's protected under the GPL, Busybox developers were able to sue them and gain some money in the process.
Interestingly enough, Tanenbaum doesn't seem to mind what intel did. But there are some examples out there of people regretting releasing their work under a permissive license.
Well, it did improve someone's live, didn't it? I'm not claiming my library that has 3 stars on GitHub is gonna revolutionize all of humanity. But it's a little improvement. That contributes to having a more complete software ecosystem.
That code is now available to everyone that wants it. If they need it, it's there to use. Better than every company having to reimplements for the thousandth time the same closed software.
Which brings me to another point I didn't mention before. If a company uses an open source library, even if they are not required to publish their improvements to the library, they might do anyway because it is easier than maintaining their own fork and migrating every upstream change.