Which is a bit weird, considering, that those things, that are contributed back, are not ensured to remain available, when anyone else makes modifications and has the option to make their changes a proprietary thing.

One would think, that if any contributions flowing back are allowed by a company, then it is to GPL licensed projects, because competitors, who want to use it in their products, would have to also contribute back their modifications. Basically to ensure, that a competitor cannot gain an invisible advantage based on ones code. (If all play by the rules.)