how do people get their projects running around without connecting to the com then?
Not sure I understand that question. If using an external DC power source via the Vin pin then also the Arduino ground pin has to wire to the external power sources' negative terminal also. If you are using the Arduino's external power jack then both the positive and ground connections are being made through that jack.
Some use USB power for the Arduino board only and use an external 5vdc DC power supply for just the servo(s) 5vdc leads and also wire the external negative to the Arduino's ground pin. That make sense?
Servos have DC motors inside as well as circuitry and their current requirements are higher then you might think depending on the servo size and how much mechanical torque is being asked to be moved.