It IS a crutch, but crutches are useful and appropriate when you are first injured. One wouldn't continue using a crutch once the leg is healed, and in fact, it could interfere with healing when it becomes appropriate to put the weight back on the leg.
As long as it's used appropriately, in conjunction with long-term treatment (which might be AA), it can keep the newly sober, well, SOBER while they are getting their feet on the ground. Not a permanent solution, as others have mentioned.