I think you're missing what's good about what the gp is advocating.
Even as a power user, I quite likely only want to change a few things "under the hood" and otherwise I appreciate a clean design. Further, the more programmers design an interface "for those other people", the more likely they are to make it purely brain dead. So you find up with two lousy interfaces instead of one well designed one (not just two interfaces take time but because you've started with the wrong attitude).
Even as a power user, I quite likely only want to change a few things "under the hood" and otherwise I appreciate a clean design. Further, the more programmers design an interface "for those other people", the more likely they are to make it purely brain dead. So you find up with two lousy interfaces instead of one well designed one (not just two interfaces take time but because you've started with the wrong attitude).