Restaurants often use steak knives with serrations because they are easier to maintain. They don’t have to sharpen them for the minimal use they get. They would have to sharpen a plain edge knife sooner or later but the serrated knife will likely stay sharp its entire service life.
Using a knife every day to make your living will cause a lot of wear on it (butcher). They’ll opt for a knife they can easily sharpen, as sharpening a serrated blade is much more difficult. The plain edge knife will also cut much smoother as serrations often tear meat.
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