Why? The hardware has been "stable" for about 2 decades now. I reckon you'd have more trouble with the IDE/USB interface drivers these days. God knows connecting an old LPT CNC machine to a modern computer proved ridiculously hard - ended up just using a very old laptop with an integrated LPT port/controller :D

I don't think it's about new features or anything, but running regular regression tests to make sure that changes elsewhere in the kernel don't break it.