Because the time and repair bill? Not many people can spend many many hours on this and pay tons of repair bill.
What makes no sense? Other HM all drop stuff that can give upgrade to most of the people. Why didn' HM EC drops 1 campaign+many Rakata or HM TFB drops 1 dreadguard+ many campaign? LI HM is the only exception.
Rule number 1 in any game is that if you cannot accomplish the objectives - you do not get loot. The fact that this pseudo "many people" of yours is spending hours on this flashpoint and paying tons of repair bill clearly makes it visible that they are not geared or skilled enough for this flashpoint. There is nothing Bioware can do if you don't L2P.
Also it's completely asinine how you don't see a Rakata chest and a Columi Main Hand as upgrade. Columi Main Hand is the absolute hardest to obtain Columi gear in the game, I have explained you this before yet you conviniently ignore facts and just continue ranting. And Rakata chestpiece is also the 2nd hardest Rakata gear to obtain. These rewards are VERY GOOD for a flashpoing that is REPEATABLE. You are given WEEKLY OPS loot in a content that can be repeatable. Continue ignoring these undisputable facts. Go on. Ignore them some more, continue ranting. Fact is all of your points have been debunked, questions answered, facts corrected time after time again in this thread by multiple people. At this point if you choose to dig your head into the sand and pretend the world is a dark place, there is nothing ANY OF US can do.