Because 15 ball rotation is basically the same animal as 9 or 10 ball. Why would anyone want to see a longer,more drawn-out version?
As if a 2/3hr 10 ball match isn't long enough already, it'd probably take a week to conclude just one tourament. (add another 4 more days if Mike Wong enters and does well)
On the other hand,1 Pocket, 14.1 or 8 ball, are totally different animals altogether and the viewers understand differences of each dicpline so they know what to expect.
Can you imagine someone trying to promote the idea of an extended version of one pocket?! :boring2: