Without knowing the exact reasons behind this, I would imagine it comes from one of two place:
- It may never have been considered when the code was written that bonds and gold should be differentiated, especially when outside the realm.
- The counting of both gold and bonds may have been intentional in order to discourage long, and long range, military expeditions outside your realm. Bring enough with you for the whole trip, and thus risk getting captured and having it taken, or don't go at all.
