The couple of times I had to go digging into the kernel what the thing looks like to me is a very large bare metal piece of firmware. As someone who writes firmware that very last thing you ever want is it to hang or reset without reporting any diagnostics. Because you have no idea where the offending code is. I'll belabor the point for people that think a large program is a few thousand lands. With the kernel it's millions of lings of code mostly written by other people.
Small rant. ARM cortex processors overwrites the stack pointer on reset. That's very very very dumb because after the watchdog trips you have no idea what the code was doing. Which means you can't report what the code was doing when that happened.