Beer and soda cans used to have removable ring-tab openers that people would drop into the can before drinking, so they could accidentally swallow it and slice up their digestive system. If they didn't just drop them on the ground to slice up people's feet.
http://westerndigs.org/ring-tab-beer-cans-are-now-officially...
>The ring-tab design began to be phased out in 1975, after injuries were caused by people swallowing the metal tabs. It was replaced with a new modification called the StaTab, which used a flange of aluminum on the lid as a lever to press down on the sealed opening, a design that’s still in use today.
https://boards.straightdope.com/t/why-the-switch-from-pull-t...
>They were a litter problem but they also hurt people who would (stupidly) drop them into the can and then choke on them, or drop the on the ground to get stepped on. The sharp edges ehre just asking for trouble. Also they were generally more difficult to open than pop-tops are.