Voltage and Current Dividers... Who does what?

Essentially, this question boils down to the equation V=IR. As you can see from the picture, the Resistance of each resistor is constant and the Current is constant for each resistor in series. This means that the Voltage varies across the SERIES circuit. 

The parallel circuit has the current chown across each resistor, which is varied. This is because each resistor shares the same nodes as the other two: the voltage is the same across each component in the circuit but the Current is variable in the PARALLEL circuit.