Many render engines will ignore back faces, this causes holes in your renders.
3d printers use the face orientation to know what is air and what is print media.
I cannot think of a reason why having back faces painted and facing out, would be beneficial.
Some times it can be useful to paint back faces because you want the inner space to be a colour or hide 'gaps' that can appear when edges are turned off, and transparent materials can be useful on back faces on occasion.