Baked potatoes, or other cooked vegetables, are considered to be potentially hazardous foods. Cottage food laws are generally only for items that are non-potentially hazardous, or in other words, items that do not need refrigeration or heat to be kept safe.
The reason cottage food laws are limited to non-PHFs is for safety reasons. PHFs have the capacity to grow harmful bacteria and are seen as being more likely to cause foodborne illnesses if the producer doesn’t take the correct precautions. I’m sure that most home producers would take the correct precautions, but it is because these kitchens are generally unregulated by the health department that they only allow sales of these kinds of foods to come from standard food businesses that make all their goods in a commercial kitchen.
My hope is that someday, people will be able to do what they always used to — make all kinds of food from home and sell it. I agree with you that it’s not that dangerous, but right now the food economy is in a state where it believes that regulation and rules are the only way to ensure the safety of our food.