Good question and one that bears repeating. Because if you desire the aspect of free software or open source that is a level playing field, where no vendor has any special status or secret sauce, which in turn is what enables vendors to submit new features to a multi vendor codebase instead of maintaining private branches.

We learned this from X11 and the Unix wars, and history repeats itself in the countless free-core-but-proprietary-enterprise-features projects that never really expand beyond their parent corporation.

This is why trillion dollar corporations must not have special rules and the playing field must be even to any use, despite how unintuitive it may feel. Someone tried to codify it early as the first of the four software freedoms (the keyword being "anyone").