As far as I know, in telephony STP or twisted pair cables are used. This creates balanced line impedances which is useful to mitigate for common mode related interference.
So using balanced cables in telephony and in audio is crucial to get rid of any EM or RF interference.
On the other hand, in TV broadcasting or many RF systems coaxial cables are used. And most of the coaxial cables I have seen are not balanced. I can see that the 50 Ohm concept is good to get rid of reflections in transmission line theory. But how come the unbalancedness of coaxial cables causes no problems with impedance balancing issues?