I don't remember any cans as tough to open as the 27-ounce cans I've opened in the last 5 years. I thought the gauge must be heavier, but I measured and it's not.
Full cans get dropped. If they dent, and especially if they bulge, consumers may reject them. If they use thinner metal to save weight, the metal will have to be harder to resist denting and bulging.
From cutting large cans, my Swingaway developed too much space between the cutter and the toothed wheel to cut smaller cans reliably. If the smaller cans are made of thinner metal, that could help explain why there's room for the cutter to push the metal out of the way instead of cutting it.
Don't tell me you're one of those fussy eaters who remove the eyeballs and scales before steaming carp on brown rice!