Why gas cylinder are round shape?

Answer 1

Well ideally a gas container would be a sphere, because the Pressure would be equally distributed over a 'mechanically symmetrical surface". There would be no structurally weaker points, like edges and corners. But for convenience, handling, and storage that is not a practical shape, but the Cylinder is next best. The round sectional shape of the cylinder has no edges or corners. The edges at the top and bottom are minimum compared to the rest of the tank. So a Cylindrical tank is good.