Why not interlace by splitting every other line of the image into two transparent PNGs (or GIFs, I guess), and overlaying them with the "invisible wall" techniq

Why not interlace by splitting every other line of the image into two transparent PNGs (or GIFs, I guess), and overlaying them with the "invisible wall" technique? There's no artifacting from refresh rates there, and the image isn't usable unless you have both.