Balanced signals are widely used in professional gear, and twisted pairs indeed reduce loop area, but it’s not perfect. I once helped out in a sound booth where the cables picked up AM radio, and some nonlinearity in the system made it audible.

> I once helped out in a sound booth where the cables picked up AM radio

This right here is part of the reason the "coathanger versus cable test" annoys me so much. All these wonderful graphs "proving" that cables don't matter never take environmental noise into account, which is frustrating because in reality that's exactly what you're testing.

The fact that you could pick up AM radio inside a sound studio means that, for experimental purposes, that environment is simply not good enough.

Are expensive cables mostly bullshit? sure. Do better cables still make a difference? My personal experience tells me absolutely yes, just usually not enough to matter to 95%+ of people.

Pro audio “snakes over cat5” seem to be thing now. Performers will probably connect their gear to the stage box using analog cables for the foreseeable future, but the big connection to the mixer seems likely to be digital in most new installations. (Just an analog snake cable, materials alone, may be more than the complete installed cost of a digital replacement.)

The mechanical design of pro audio balanced cables is poor and it's common to end up with a bad one in the field. A balanced amplifier with one input connected to a long unterminated wire is way worse than a single-ended cable would be under the same conditions. Even in consumer home use XLR cable ends will fail. We're stuck with it unfortunately unless you want full custom gear.

Genelecs and other pro-audio gear can get their signal via AES/EBU. Digital all the way through the chain up to the speaker is fantastic!