It&#x27;s the same reason other interesting things don&#x27;t get mainlined from time to time: personalities and opinions. Linus is a loudmouth and he has every right to be like that. It&#x27;s his playground after all. But this leads to blind spots and dogmatism in areas that ultimately hurt the project.<p>In case of grsecurity Linus tends to disagree with their philosophy of what leads to more secure system and what doesn&#x27;t. And if Linus thinks you&#x27;re wrong, then you&#x27;re wrong, period. So grsecurity crowd would have to bow and compromise (which collides with their philosophy) on what stuff gets integrated, how, etc.<p>What&#x27;s good enough according to Torvalds is not good enough according to them. But let&#x27;s say they kneel. They&#x27;d have to not only cut their baby in pieces and massage it over and over again, discussing every detail of design and implementation on the list for Linus to mercifully accept it, they&#x27;d invest time pleasing him instead of doing what they care about: improving security.<p>So it&#x27;s a lose-lose for them. And mainline doesn&#x27;t seem to care about security (contrary to popular belief I guess). So yeah, there you have it.