Because the faster runner will almost always win an 800. No matter which way you cut it the 800 is too short of an event to not have speed in and excel at it. If it is a tactical race (slow), then fastest runner will win. If you can’t produce a fast first 400 then you can’t stay with the leaders to win a fast race. This is the event that I try and push my mediocre sprinters towards. There is significant reasons to tying an 800 event to the 200 speed. As for 1500/1600m races the need for speed at the High School level is not always essentail, but it is rapidly approaching that point.