Why in some Communication Protocols the Wires are twisted?
Why in some Communication Protocols the Wires are twisted?


It's called twisted pair and it's a method of reducing EMI from the cable and making it more resilient to EMI that it receives. 

Consider the emission scenario - if the wires are side-by-side (in a plane) then there will be a measurable far-field magnetic disturbance (due to wire signal currents) all along the plane of the wires until you reached the exact centre between the two wires. At the centre, the fields will be equal and opposite.

By twisting the wires you are repeatedly swapping the conductor positions and thus the far field magnetic field is significantl reduced. Consider these three scenarios: -



It's the same for the electric fields too providing you are driving differentially. They even do it on old overhead telephone wires to prevent crosstalk to other subscribers: -




  For example in I2C: SDA and SCL?


If you mean why are SDA and SCL twisted together then this answer doesn't cover that and I can't explain why there would be an advantage.