172 driver,
They are very aerodynamic, even more so today with the ability to manufacture shapes not before possible. Not only that, there is less of them in a rotor doing more work than when there were 1/4 or more in a rotor.
As fat as ice observed on fan blades doing a walk around, it is somewhat subjective as I recall seeing photos on a PPRuNe thread that depicted ice on the back of the fan blade that is hard to visually observe...