This sounds all roses and sweetness but the reality is, surgery involves volatile hours. Some degree of predictability may be known, for example weekend nights probably have a greater probability of road accidents, but for the most part, surgeons have to perform at a moment's notice to save lives.
Whilst you could simply employ more staff to ensure there's a healthy buffer of refreshed and well slept surgeons, I'd hazard a guess this is far more costly than most hospitals could afford or would want to cut into profits.
Declaring sleep deprivation might make some academic journal tingle inside, but how will that affect lives? You get a disclaimer and a law suit potentially sidelined. But the patient then must wait for a suitable surgeon to perform. In many locations, that simply might not be an option.