The recently-released NES Classic Edition has garnered praise from all corners, but many users have pointed out and criticized the very-short length of its controller’s cable. A likely reason for this has to do with the controller using the same communication protocol as the Wii Remote, which was apparently not designed for long distances. Read on below for a more in-depth explanation:
The communication protocol used is I2C , this protocol was designed in 1982 by Phillips (now NXP) and was designed for “high speed” chip to chip communication, it does have some limit for the actual standards , first is the speed, second is the length, according to this the length of the NES mini/Nunchuck is right 50pF , which is the maximum you can get from a yet-flexible cable.
So, why they didn’t make a thicker cable? Because would have been more expensive and less practical.
And what about the extension cables? The probably works but are pushing the limit of the protocol, you probably get some communication errors but you don’t notice them while you are playing.
Why Nintendo didn’t use another communication protocol? Because otherwise they would had to make a new set of controllers just for the mini, not compatible with the wii and wii u which is an expensive procedure, design and manufacture the connector itself is really expensive and the NES mini is a small product for Nintendo.