Actually, most canned cat food has those pull-off lids as well.

This is convenient when you're opening them, but the ring of metal that's left has a sharp edge.

Just about the time this feature came out, towns started trying to recycle trash - including metal cans. They request that cans that are recycled be cleaned out first. This almost necessarily involves sticking fingers inside the empty cans.

Eventually, you learn how to do this without cutting your fingers very often. But you lose a good deal of blood in the learning process.

Speaking of pointless features - since the creator, or evolution, created men's nipples, he/she/it must be in favor of them...

Peter