I think the obvious one is that the Linux kernel is no small little project, and any tree-wide change is highly non-trivial. The compressed current source relea

I think the obvious one is that the Linux kernel is no small little project, and any tree-wide change is highly non-trivial. The compressed current source release is 138 MB. A 2021/5.11 lines of code figure I found was 30.3 million. It's not impossible, but the Linux kernel is quite a complex project.