Yeah, one usually records the sources in mono and uses panning during the mixing process to place the instruments in the stereo sound stage. Stereo recording is often done when trying to capture the sound of a real, good-sounding acoustic space, but it's much more difficult and sophisticated to record that way.
There is no point in recording two copies of the same data on both the left and right side. It will come out in the middle, but it sound identical to a mono source panned to the center, and take up twice as much space on the hard drive. And, if you do want to pan it to adjust its place in the stereo image, you'll have all kinds of troubles.