I noticed the same thing… and I also found some fine print on my Denon, paraphrased as: “at least 80% of rated power delivered to all channels simultaneously”… IOW, 75x2 becomes roughly 55x7.
I’ve always wondered (and am by no means an amplifier designer or builder), why one wouldn’t transform the power up to maybe 1kV before feeding the circuitry, and then current would be greatly reduced, the amp would run cooler, and there would be more headroom because you could then make say 1000W at 1A, vs roughly 8.5A on 120V.
I’m sure consumer safety is a big factor, but there have to be ways you could protect the circuit from powering up if the guts were exposed. And yes, I know, all of the other components would have to be similarly uprated, which increases cost and complexity.
Everything is a balance of performance and features to hit a given price point, and these days it just seems like so many people are “satisfied” with a portable battery-powered Bluetooth speaker that likely struggles to make a clean 6W, so manufacturers say, “fine! We’ll make a semi-sucky product for about $23 in parts, spend $100k on product placement advertising, and charge you $150 for it!”