[millstone]

Those real life tools have a far simpler interface than, say, a mail client. As software becomes more complex, HIG increase in importance, because there is more to learn and HIG enables us to transfer knowledge across apps.

[Turing_Machine]

The actions you perform with a scalpel (or even a bulldozer) are far more complex than sending email, so arguing that they have a simpler interface doesn't really support your case. Quite the opposite, in fact. I would argue that they have simpler interfaces because those interfaces are actually optimized for the task, rather than being some jack-of-all-trades compromise.