As I follow a low carb approach I have found that when I go out for a meal, I can typically only eat half the meal, ie just the protein/meat part and the veg! I have got used to leaving the starchy carbs behind, and I seem to get as full without them as in the old days when I ate the carbs and the non carbs, so I don't see it as a massive waste. BUT recently I have started asking for extra veg instead of chips/rice/potatoes and most places will willingly oblige. I just say 'I can't eat chips can I have some extra salad please' and mostly they will just charge the same as the original meal, plus it means I don't have to leave half the food on the plate.
But I remember at school being taught that a balanced meal had protein, carbohydrate and vegetables in it This coupled with the fact that most starchy carbs are relatively inexpensive compared to the protein element may explain why it will take some time before restaurants put low carb dishes on the menu