Why do recipes never seem to turn out right when you halve the recipe?

If it is cooked or chilled for a certain time, is cooked that way to make that size portion get cooked correctly. E.g. If you cook a steak (sorry, its the easiest example), the recipe's cook time will make it so there is a certain amount of well cooked meat on the outside, and less cooked meat on the inside. If you cut it in half, there will be more cooked meat than 1/2 the regular amount, and less... well, less cooked meat than 1/2 the original amount. Hope this helps!