And the answer is.....
Even though steel is hard, it is malleable to a small degree. The bearings touch and roll on a point. However, surrounding that contact point is an area of incidental contact where the two opposing surfaces "scrub" one another. Imagine a fuzzy donut image surrounding the contact point. It's this metal-metal rubbing around the actual rolling point that requires lubrication. Ceramic bearings are significantly harder and less malleable, and thus do not have this surrounding scrubbing contact area. How's that?
I thought it was in intriguing question because, after all, bearings are ROLLING. You'd think that a high-quality precision bearing wouldn't need lubrication. But it doesn't matter how high the tolerances are if you'll always have the "scrubbing" effect.
Well, now remember I'M not the engineer, so don't jump all over me if I'm not completely, technically correct. All the posts seemed to come pretty close, especially the issue of micro spot-welding and the need for hydrodynamic lubrication. Also the need for corrosion resistance would necessitate using grease (or other hydrophobic lubricant) in steel bearing applications.
Thanks for reading and happy trails & roads to you all!