ActionScript 3.0 :: Custom Events - Any Way To Call Function?

The fact is that the "dispatchEvent" method must be placed into the code or timeline where the "event" happens, then it can be trigged and the function associated with the event will be invoked. Ok, it is understood. Nevertheless, my question is: what's the point to create an event to trigger the a function call, if I can simply call the function instead directly???

Code:
package{
import flash.events.Event;
public class CustomEvent extends Event{
public static const ONSOMETHING:String = "onSomething";
public function CustomEvent(type:String){
super(type);
[Code] .....

If I can do simply:
Code:
DoIt();
function DoIt(){
trace ("Done!");
}
What I mean is that custom events doesn't look like as REAL events for me, but more like a delegate way to call a function. Differently from Flash native events that are controlled by an internal engine that keep checking if the event happened, in the custom events they must triggered 'manually', and it seems to lose the event main characteristic.