Being somewhat chronologically advanced, I had to use those clunky old single-blade safety razors for many years (and would nick and cut the heck out of myself) until the advent of Gillette's two-blade razor 20 or so years ago. That revelation was followed by the three-blade Mach 3 about a decade ago, and now Gillette has introduced the six-blade Fusion.
The Economist asks whether there's Moore's Law for razors. In other words, is there a limit to how many blades can be packed into the head of a razor? The answer is here.