I had always thought of bouillon cubes as more of a morale issue, as hikemor mentioned above. In a wilderness or outdoor situation, the ability to sit down and have a cup of broth as an excellent way to "Relax and refresh" while taking a mental break. Tea is also an excellent possibility.

Just looking at the nutritional info on Wyler' brand of bouillon cubes:

1 cube
6 calories
<1 Gram protein
<1 Gram fat
1 Gram carbohydrate
Sodium 930 Mg.

Have to agree with jshannon, an amazing amount of Sodium.