Cancellation
Transmitting cables have a naturally created magnetic field around them.
When two wires are placed in close proximity, their electronically created magnetic fields cancel each other out. This cancellation actually insulates the signal from the effects of signal bleeding.
When the wires are twisted around one another, the magnetic cancellation is enhanced.
The twisting of the wires not only protects the signal inside from internal crosstalk, but it also protects it from other external forms of signal interference.