Heh, when I started rolling my own kernels the first matrix movie was still kinda recentish and my computer still had a 3.5" disk drive it could boot from. I saw some "linux router on a floppy" thing that greatly impressed me and learned to cut away bloat and build a kernel tightly set to my hardware. In these days, it did make a noticable speed difference to do that, alone because a smaller kernel loaded faster from the IDE HDD. Less to load!
I still roll my own kernels in Alpine. It has not much practical use anymore, besides fiddling with the initramfs to be able to (un)lock computers remotely in a specific way And applying some (small) patches when needed, but it's also a way to keep the finger on the pulse of developments and changes. You get an idea for the direction the kernel is taking and look at the changelogs and develop a feeling for which parts the maintainers struggle with and which minor releases are the problematic ones. You also learn how the different parts of the kernel come together, what (new) it has to offer in the way of APIs and what does what. All things you could also look up without rolling your own, but if you are not forced to do so you usually simply end up not doing it, at least I am that lazy. This stuff is like a muscle, you need to exercise it or it goes away. That's why I also don't think it is useless to do all this low level stuff. You will always at least learn something. If I didn't do all the "useless ricing" in my Linux blunder years, I would not know what I know now. I'm not sure when it became uncool to know stuff, but I find that general attitude quite unsettling.
