2.2k ohm on 5v line in Snes 1 chip with switches: necessary?

I used to always put 2.2k on 5v in this mod, but is necessary?

I'm pretty sure to have forgotten to put that resistor one time and everything worked fine

 

If I remember correctly, it is a safety resistor. It would prevent excessive current flowing through the line.
We want just the 5V signal, not any current. Current might flow when doing the switchover when the console is on.

 

The 2.2k ohm resistor is to limit the current during switching with a manual switch. There is no need to have the resistor with an electrical switch like a microcontroller.

 

but why is used on snes and not on other consoles like mega drive? (im totally ignorant about electronics theory)

 

It should be used on all such mods. If it's missing for other consoles, then it should be added.