Most of them at some point have been stung by finding a library that perfectly solves their problem, only to notice that it’s licensed GPLv3 (or similar) and thus the legal dept won’t let them touch it with a ten foot pole (and/or interfacing with that dept is not worth the bother). They’d rather not put others in that predicament and want their work to be useful to as wide of a spectrum of devs as possible.
Both copyleft and copyright (to a lesser extent) are in opposition to my beliefs and goals.
I figure it's because the companies and orgs that started working with and investing in the rust ecosystem start by contributing to the compiler, which is non-copyleft and just try to extend that because it works to their advantage. You see this with a lot of languages/ecosystems with corporate sponsors, but also just because it gives you a unique selling point in an area where copyleft software dominates. Like, there will always be some company (like imagine a defense company) that absolutely refuses to publish all of their changes, so that represents a niche that can sustain smaller permissive projects.
I think that for an individual corporation, permissive is better and they won't make a decision to go copyleft unless forced. But for the ecosystem as a whole, GPL is better for business (especially when it comes to something like a kernel) because it forces companies to publicly fork over their drivers and collaborate, and reduces the competitive advantage vs companies that would otherwise not publish their changes if it was permissive.
That was probably too many words. Anyways, it would be nice to see some of this improved, i think it's a great language and will probably replace C++.