We've move up the stack. Kernels are a lot more developed than they were when the author was a kid and in the present day there's a lot less to be gained by wri

We've move up the stack. Kernels are a lot more developed than they were when the author was a kid and in the present day there's a lot less to be gained by writing your own / hacking on an existing one. His kid will hack on something else even more interesting higher up the stack.