I was just watching Netflix comfortably when I had to ask myself the question WISO are the shifter cables / Bowden cables exposed but the brake cables mostly not? Is there a logical explanation for this?
If you drive the shifter trains away, you can never switch.
If you get stuck with the brake cables you are dead in the worst case!
Everything inside would be even better. But laborious
Okay, I didn't think so, I thought there was some "more logical" reason like looking at the condition of the cables or something
Force and counterforce are always related. The sheathing absorbs the opposing force of the cable brake. With the shifter, this can be done by the fixed frame. You will also find a casing for sprung bikes.
With the brake cable, the cable casing can just as well be guided to a stopper and the brake cable can be guided "naked" between the stoppers.
I wouldn't say that "most of the time" is. I know all combinations of partially exposed trains and completely continuous shells. In general, trains with continuous hulls are better protected from dirt and corrosion, so they slide better over the long term and do not have to be replaced as often. Instead, the exchange can be more complex.
What you may not have considered are hydraulic brakes. Of course, the line has to go through with them.
