Never mind the naive logic behind this question. Never mind the question. I think there are definitely more 400m runners than 800m runners in the world. Why, you ask? Well, a 400m runner can likely run a reasonably fast 100m/200m or move up and run and 800m. World class 400m guys can't do as much, but in high school/college running, a 400m runner could essentially run the 100, 4x100, 200, 4x200, 400, 4x400, 800, 4x800, SMR, DMR, 300, 400, 500, and if they're really talented, 300/400 hurdles. 400m runners will typically have the most range for events, and thus are the most likely to score more points/win more races at a track meet than any other runner. So, there is a chance that a 400m runner that had the potential to rewrite the world record never ran the 800 to his full potential, that is probably the reason why: they went for quality instead of quantity. Or they just didn't want to run such a painful event.