[Furface]

That's an interesting thought - and even if they (we!) do branch out into the longer distances, the depressing (in both senses) effect of moderate technique means that one's handicap does not get affected.
So this will also explain another phenomenon, that the Classification becomes a better indicator of progress than the handicap, even though it is less granular. I can think of at least one recent compound archer at my club who reduced his handicap greatly, but usually when he shot Short Metrics for postals. Has since given up, after the frustration of not being able to match his handicap at FITAs.
So, thinking on the paw, those perenially stuck in the 50-40 handicap range are probably better served by a complete technique overhall than a more evolutionary approach. And this would probably benefit from using a weaker bow, rather than the more frequent approach of getting more powerful new equipment, which would only hide poor technique.