The first tin cans of food were manufactured around 1813. The first can openers arrived more than thirty years later.
Food preservation was big business, especially for armies, navies, and polar expeditions. The first tin cans were a huge step forward, sealing food and keeping it free from microbes and decay for years.
(Side note: they work really, really well. Cans of food from 1865 were salvaged from the shipwreck of the Bertrand steamboat and opened in 1974. They were safe to eat. Although do you really want to be the one to try 109-year-old canned oysters?)
Those first cans, though, were big, heavy, and sealed with lead. Delicious, nutritious lead. And difficult to open! You had to use a hammer and chisel, or some other similar tool. The first tin cans just weren’t common enough, or cheap enough, to warrant the invention of a completely separate device just to open them.
Once tin cans hit the mainstream, inventions to open them easily finally showed up. The claw-lever openers were patented in 1855; the rotating wheel can opener appeared in 1870, although the second wheel wasn’t added until the 1930s – funnily enough, it was patented the same year as the first electric can opener.