Even Paul McGowan of PS Audio (infamy) doesn't think that impedance matching is a thing anymore. Like so many audiophile myths, it comes from the days of vacuum tubes and output transformers where it made a difference. Most modern equipment has near 0 output impedance and near-infinite input impedance (thank you opamps!). I think there is also some trickle-down from concepts that are important in the RF world but have absolutely no implications in the audio band.
There's a historical perspective to impedance matching, and it does apply to audio, going back long enough. In the early days of analogue telephony, voice calls were routed as baseband audio signals over open wires hundred of metres, even tens of kilometres long. To avoid reflections which would make speech unintelligible, the sending amplifier had to be impedance matched to the transmission wires, which had to be matched to the receiving amplifier, and 600 ohms was the impedance of the open-wires. This was later applied to broadcasting, where again the cabling from the studios to the transmitters was done with equalised land-lines where the sending and receiving impedance had to be matched to that of the line. Within a studio, it may not have been necessary, but as cables could be of any length, even inside one building could have hundreds of metres, the practice was continued, especially as equipment was often located in racks a long way from the actual studios.
In more modern times, where studios were more self-contained, there was much less need for impedance matching, and bridging became the norm, where the sending impedance is low, and the receiving impedance is high.
Once HiFi got going domestically, there was never the need for impedance matching, and even the earliest home audio equipment had low(ish) sending impedance into a high receiving impedance. With tube preamps, if they didn't have cathode follower outputs, then the sending impedance was typically around 10Kohms, but receiving would be around 1Mohm, so as long as the cable was short, say 1-2 metres, the HF response would still be adequate. The better preamps had cathode follower outputs which could have output impedances of a few hundred ohms, still much higher than today's, but still low enough for quite long cables.
S.
