I dunno, havent played since Wotlk and just seems crazy that you have 4 chances at loot, even if some are worse/much much harder to get than others.
Eh, you won't find many people that are doing all the difficulties. "Real" raiders probably won't even step foot in LFR unless it's to finish the legendary quest faster. Normal is tuned for people who have normal dungeon gear, Heroic is tuned for people with heroic dungeon gear, and Mythic isn't even open until next week.
You might have people running the lower difficulties in their off time for extra gear, but it's not really necessary.