IIR, that optimal cylinder assumes that the cost per unit area of the sides is the same as the top & bottom. A can of coke - or beer, or other carbonated & pressurized beverage - breaks that assumption. The curved sides are mostly supported by the pressure of the contents, and can be far thinner than the top and bottom.

But commercial success is much more driven by consumer preferences than by optimized packaging. So don't expect to see many tall, thin coke cans. (Which may tip over too easily, feel odd in the hand, slosh when one takes a quick drink, etc.)