Why are aluminium soda cans typically round instead of square?

Why are beverage cans usually round? Considering the amount that are made, and the need to be transported - isn't a round design inefficient? (ie the lost space from not tightly fitting together).

Is there a usability impact on a round can vs a squared can for one handed drinking use?

There is a related question here but I believe the physical properties of aluminium mean there is a difference here.