stupid rudder question

If rudders and skegs do the same thing, why do rudders have side-to-side directional control? Shouldn’t it be enough to simply drop the rudder into the down position? Clearly I’m missing something here.

rudder vs skeg
A rudder gives variable steering input in the direction of choice, much like a steering wheel in a car controls how sharp the turn input is.

A skeg merely counters weathercocking. Its steering effect is controlled by moving the skeg up or down. Its effect is a fairly coarse adjustement.

A well designed rudder adds minimal drag, and a very high degree of control. Typically, in racing boats, the penalty is about 2-3% of wetted surface, about 1-2% of overall drag for racing hulls.

I forgot about racing boats
In connection with the non-racing world, I had understood that rudders were to counter weathercocking, the same as a skeg. For example, on the boats of the New Zealanders who rounded South Georgia.

rudders provide more steering control but are more likely to come out of the water when it gets bumpy—stern lifts up and suddenly rudder isn’t in the water—can happen to skegs too but not as often

Nice, tough, rough sea expedition kayaks.