And to be fair, putting graphics stuff in the kernel allows Windows to do some graphical things properly, like a secure attention key (ctrl-alt-delete to log in) and a proper task manager.
Linux can't really do either of those things nicely because graphics is just another program. Although I'm sure you can isolate your don't decoding better than shoving it in the kernel.
The secure attention key is handled or if you will caught in the keyboard driver, and then sent to Winlogon, a user space program. How does that relate to graphics being in the Windows kernel?
Well kernel development is not my area of expertise, and I haven't done even any Windows development since before 2009 so ancient history in the recesses of my mind, but I would think that since the SAK causes the secure desktop to appear then there needs to be graphical connection there?
Probably I'm wrong in that supposition there, but then what happens?
Euh, I think a secure attention key is fine; you only have that chord sent to a designated trusted process; preventing other processes from being able to react to it and mimic an auth dialog.
You absolutely can do secure attention key with just another program. If your account does not have /dev/input permissions, only your display server has keyboard access (unless you run stuff as root lol), and handle key combos that force some secure thing to happen.
Linux can't really do either of those things nicely because graphics is just another program. Although I'm sure you can isolate your don't decoding better than shoving it in the kernel.