What are the advantages of steel tubing?

In some cases, depending on the size and weight of tubular steel pipe vs the same or similar size solid steel bar, the tubular steel might be stronger. The molecular structure of the solid steel have the molecules stacked close together, any shock or stress will compress the molecules closer together with no place to go unless the steel bends or breaks. A steel tube has the hollow area which allows shock or stress to be released, it will be less likely to bend or break. It also depends on what the application is tubular steel will definitely be lighter in weight, can be filled, run wiring or plastic tubing through it. Cost is cheaper.