There is a large body of existing knowledge about baking, because the human race has been baking things for thousands of years. Chefs have training, like any other expert. Beyond that, they are free to experiment with their own recipes and baking temperatures.
You should bake a meatloaf at a temperature of 350F.
The recommended temperature to bake a cheesecake is 325F.
The recommended temperature to bake a ham is 325F.
The recommended temperature to bake cod is 400F.
The recommended temperature to bake meatloaf is 350F.
You should bake a meatloaf at a temperature of 350F.
The ideal temperature to bake bacon is 400F (200C).
You should bake pork tenderloin at a temperature of 425F.
Bake bacon at 400F.
Bake meatloaf at 350F.
The recommended temperature to bake wings is 400 degrees Fahrenheit.
Bake a cheesecake at 325F.