To make my point let me begin as simply as possible – cooking with water. Heated water is an excellent medium for cooking all sorts of foods: pasta, potatoes, eggs, and even meat. When we use water to cook meat (e.g., braising) we typically call the result a soup, a stock, a stew, or a pasta sauce – all wonderfully delicious end results. While the virtues of cooking with water are seemingly endless, water has one serious limitation. It only reaches a temperature of 212° F. That's certainly high enough to cook any ingredient I can think of, but really special things happen when some foods reach much higher temperatures.
Non-aqueous liquids, fats or oils (chemically called lipids), comfortably reach much higher temperatures, typically 450° F and above. Oils generally begin to smoke before they boil, so their smoke point is the maximum practical temperature that can be used for cooking. When meats, for example, are heated to temperatures over 300° F, the amino acids and sugars in the meat begin to change into complex sugars via a process known as the Maillard Reaction (named after Louis Camille Maillard, who discovered it 1912) . The result of the Maillard Reaction is deliciously browned meat!
When vegetables, again for example, reach temperatures in excess of 300° F, the chemistry is different, but the results are similar. Browning (again) occurs, but this time because carbohydrates are being converted into complex sugars via a process called caramelization. As with meats, the result can be spectacularly delicious.
In both cases – and this is the point of this entire discussion – wonderful new flavors are introduced into these ingredients by the mere application of "extra" heat!
There is much more to say on this topic, but I will give both of us a break now, and then call the continuation Cooking 102!