[londons_explore]

"Nurishment" cans, often found in the foreign foods aisle, still use the old style ring pull.

I'd guess it's because they are intended to be drunk like a soda can, but packaged in a tinned-sweetcorn style can. Those cans are unpressurized, use steel, and have significantly thicker walls (= more material cost)

I do wonder why they never decided to switch over? Perhaps they consider it part of the brand? Perhaps they still run the same canning factory for decades and without expanding sales don't see a need to retool? Perhaps the 2 pence per 1.50 product are insignificant when they have quite a market niche.