I know a bit about this. It isn't chipping of the blade. Honestly, how often does that happen - especially to a professional who knows every single cut? It also isn't cost effectiveness, since I've seen butchers that will spend $300 on a knife that is 57hrc. What it comes down to is the razor edge that is needed to cut meat, and the process of cutting the meat. A regular knife that we all use at home is harder because we use it, wash it, and put it away. Rarely do we use the honing steel, thus they make the knife harder to require less maintenance at home because that's what the major market desires - a knife that is easy to take care of and holds an edge. Most consumers have no clue how to use a steel, and most also have no clue that it DOESN'T sharpen the knife. It just straightens the edge. The butcher, on the other hand, is constantly using his steel. The reason is due to that soft blade steel, but it goes deeper than that. As stated before, the steel only straightens the edge on a normal hard kitchen knife, but on the much softer butcher knife it actually will do minor sharpening as well. This is the key. If the butcher uses his steel properly, he will always have a razor sharp knife that he needs to do his work. Certainly he could buy a harder knife and just use a ceramic steel, but keep in mind that this would remove quite a bit of material; plus the constant cleaning of the ceramic, risk of breaking the rod, etc. The honing steel is the best method. It removes so little that the knife lasts forever while always being maintained. This is why butchers use softer knives, and it's also why they constantly are wearing a honing steel and use it every 4-6 cuts. Some people would believe this to be tedious, but honestly it becomes second nature to the butcher and his knives are always razor sharp.
