Comment by Animats

That, plus the ability to rotate, pan and zoom while you're in the middle of a selection. That's a huge win. In 3D work, you often need to select 2 or more things, and those things may be small and need precise selection. Precision multiple selection is hard.

Before this was worked out, most 3D programs offered four panes, with three axial projections, usually wireframe, plus a solid perspective view. Just so you could select. Now we only need one big 3D pane.