Having a response that is smooth above 20 KHz say up to 25 KHz and then rolling off nicely is a benefit for phase coherence at lower frequencies - in the analogue circuitry. The filtering post-DAC will determine the actual audio bandwidth. Anything above 20-odd KHz is however inaudible, but one likes to do it right. Response much above 20 KHz is entirely irrelevant to your hearing which even when young will not extend above 22 KHz - mine went up to there when I was 22 and I went unusually high (I was a studio engineer). At 73 it extends to 11 KHz. It makes little difference, there is no music to hear up there. Just "air" i.e. harmonics, and most of that is loudest at 6-10KHz rolling off at say 12 dB per 8ve above that. And that is the case despite what deluded nonsense some commentators come up with - I'd love to see them in a blind A/B telling the difference, but that won't happen. Do note that as GA Briggs said, and as I have quoted before, "the wider you open the door, the more the muck blows in". Bandwidth limits, within limits, and in the right place, are good for fidelity. Outside of classical recording, modern mixing and mastering often adds HF compression to the signal to emulate tape compression, modulation distortion and tape's limited HF capability...