Electric Shavers Vs Razor
You know this intrinsically, but consider it again: The sharpest razor is just a few molecules wide at its edge, persuading the molecules it meets that it would be easier to decouple from their mates and let the razor pass through the space where they once twisted and wound together.
So if a razor is such a simple mechanism, why are there so many different types?
Perhaps the razor's simplicity lends itself to many configurations? A screw is a simple object, but there isn't just one type of screw, but countless variations to suit the needs of its user.