Resistor required for capacitor?
Well, you know that to charge a capacitor instantly will require infinite current, right?  And we know that all real-world power sources have some finite resistance  associated with them, as do capacitors (ESR).  However, as your intuition suggests, if you just pop your capacitor across a supply you are depending on the parasitic resistance to limit your current.  If it doesn't limit your current enough your supply may not be able to handle it and you can get droop or brownout.

So it's better to control the charging impedance to a known value that doesn't stress the rest of the system.  

Sometimes, especially in AC/DC supplies a positive tempco thermistor is used to limit the inrush that charges the main cap.  As it heats up the resistance decreases and the circuit begins operation.