Structural metal tubing is normally used to take bending, axial and shear loads, i.e. to globally transfer load from one place to another. It also has to resist local loads, i.e. if there is a concentrated force or impact force in a particular location, the member has to not buckle locally. In other words: bending shear and axial and taken by (more or less) the whole cross-section; local loads are resisted by parts of the cross section, and they are then transferred into the whole cross section.
Bending and axial loads travel down the outside walls of a hollow member. Internal bracing won't make any difference to this.
Shear force and local loads travel across the cross-section. Internal bracing could help with this.
In my experience as a structural engineer, the critical factors governing design are normally bending and axial force. Sometimes shear is a controlling factor in cross-section selection. I can't think of a single instance when local loading has been of any importance to a structural hollow section. (NB I work in bridges. Local impact may be of more importance in other disciplines.)
Therefore, when you're using "standard" structural hollow sections, I find it unlikely that internal bracing would be beneficial. And the cost of adding it would make it uneconomically viable.
There is, however, one aspect in my experience where internal bracing is required. That's when fabricating a steel box girder. These use relatively thin plates spaced a long distance apart, and in order to avoid buckling they need to be braced, internally, at regular distances.
