Why does a IR Transmitter need a VCC?
Ideally, the IR-led is powered by a VCC line, capable of delivering the ~60mA a infrared LED generally needs. This should be done by a MOSFET, which is essentially a switch, which switches on and off based on the data line, which is connected to the gate. 

In the case of your IR transmitter, no MOSFET can be seen. It means that the IR-led is directly fed from your data line. It works, because your data source can deliver enough current. It's generally not the way you'll want to switch an IR-led on and off. Hence the fact you can detach your VCC line: it's not being used.