This isn't always possible though. If you are running a long cable to a mixing board, for example, it's virtually impossible to ensure the same ground potential at both ends of the cable. Balanced (i.e. XLR) cables are ALWAYS the best choice for these scenarios. 1/4" cables should only be used for short runs between equipment. If you must use 1/4" cables when connecting equipment plugged into different outlets then Humbuster cables should be used.
As I said …. a good
starting point to avoid hum loops.
Certainly there are a other remedies to avoid or cure the problem, too.
Balanced audio lines are
always the best choice for analog audio lines. And I am quite certain everyone agrees.
But hum loops are some times tricky nasty and can introduce in several ways. No problem to solve if you have time to. But if time matters I prefer to be on the safe side.
And indeed for decades now I
always have the FoH mixing desk running on the same ground potential as the audio stage equipment running in front of the FoH mixer.
For locations with audiences up to, say a few hundred, it‘s very easy to do. Simply add just one power line to the already existing network audio line (in earlier decades: the multicore) between stage and FoH. That’s is - and gives you a lot of additional certainty to avoid hum problems.
You might correctly argue that the resistance of the long power line influences the ground potential in a similar way a long inhouse power lines does.
On the other hand I‘m in no way aware of the status (phase, grounding) of the wall plugs I find in a certain location. The status of my power line between stage and FoH mixer I know and can trust in.