Food, especially fresh food, used to be a lot more expensive when adjusting for inflation. A canned chicken like this doesn't look super appetizing right out of the can, but it probably tasted OK after you shredded it and put it in a casserole. And it was significantly cheaper than buying a fresh whole roasted chicken, assuming you lived somewhere that fresh whole roasted chickens were even readily available. Food like this became particularly popular during the great depression, and stuck around for decades afterwards.
Nowadays, between industrialized farming, highly optimized supply chains, and a buttload of government subsidy, fresh food is comparatively cheap. You can get a whole roasted chicken right off the spit for $5-10 at just about any grocery store. So for most people the value proposition of a $3 canned chicken isn't really there anymore, especially if you don't have an enormous baby-boom-era sized family to feed.
Emmymade on YouTube did an “Apocalypse Dinner” featuring these whole canned things, the chicken, brown bread, and cheese being the subjects of the video.
She’s pretty fun and tries out some odd stuff occasionally, but this particular episode stuck in my mind as I’d never seen one of these prepared and eaten before. She also has Apocalypse Breakfast, Hamburger In A Can, among others.