When I read this, my first reaction was to think, "yeah, but how often do you really do any kernel hacking?" But actually, I've been on teams that have done all of the following:
* run a patched version of PHP in production
* run a patched version of the Squeak VM in production
* run a custom-built Apache in production (no patches, but highly-tuned build configuration)
* run a patched version of the OS X automounter daemon for office infrastructure
Ok, it's not the kernel, but it's fixing problems and implementing features at the right place in the stack instead of working around them and waiting for a vendor to ship a new version. I'm not the right guy to do kernel-hacking, but I know that those people are out there and I can hire them to do what I need, if it should come to that.
So, sure, it's cultural. But part of that culture involves not being enthused by the idea of waiting for Microsoft or IBM or Oracle to fix a problem that's affecting my customers now.