Being open for collaboration does not mean anyone and anything is welcomed. But I could just write to the kernel mailing list (I think, it used to be like this) - but yeah, since I am not a kernel hacker, I do not have anything meaningful to contribute, I would be ignored, or told to shut up - as it should be. I won't go there and say "hey you know, it would be really good if linux would support xyz ASAP". I have no right to do this and this would not be welcome - yet in many other open source projects, this is quite the norm. People come with this expectation. Some even might have donated 5$ and think now they own the place. Well, no.