Why can't challenge mode drop better items?

I think it's cool and all that challenge mode give achievements, mounts and transmog gear, but theyre just all for show, why not have them drop some significant drops? By that, i dont mean a whole new tier of items that everyone will want to farm before raids.. let me explain.

Remember in BC and Wrath when you were farming heroics for that one epic item on the last boss? It was no gamebreaker, but having a sun eater definitely helped you out, farming those specific items were a fun goal to accomplish as a guild.

What i suggest, is if your group can finish the challenge mode dungeon on silver, or maybe even gold, a random epic will drop from the last boss, just like in the old days of BC/Wrath final bosses, something equal to regular raid difficulty in ilevel. Perhaps the loot table could be shared amongst all the challenge modes, so you wouldnt farm one in particular, or maybe farming one in particular is a great thing too.

This way, beyond clearing the challenge mode and getting achievements, you add a farmability to those challenge modes. The more friendly guild groups will want to farm them to get the 2-3-4 epics they can get to help them through progression, it adds something to do in the endgame, and doesnt create a massive disparity between casuals and hardcores since its only 2 to 4 items. On top of being in the hardest difficulty of 5man this game has to offer, its a great deal for better players.

I'm sure im not the only one who misses farming one heroic everyday for his sun eater or red sword of courage : P