It has to do with the highly non-linear Current vs Applied Voltage curve of the LED vs an Ohmic device like a resistor.
Btw- resistors do NOT PASS current in excess of what they NEED!!! The current never flows because the current is the dependant variable; i.e. it is the RESULT. The CAUSE of current flow is the VOLTAGE applied to the resistor, and the Resistance in the circuit.
I think we may not understand eachother.
I just meant that you could connect an IC's VCC pin to a source of power without a resistor to limit the current. Isn't that right?
Also what do you mean "The current never flows"