Because regular raiding is a waste of my life, and WoW endgame is one huge grind. I just want to experience the lore, don't care about wasting hours of my life fighting imaginary monsters that we can't kill because our tank doesn't have some shield yet and our healer doesn't have some trinket.
LFR: get in, experience lore, get out.
Regular raiding: get in, waste time on bosses that you know how to kill but can't yet because your raid isn't geared enough, waste time farming gear from lower bosses.
WoW "endgame" is a joke, no better than GW2 or anything else, always was. Wasted monumental time with it in BC/WOTLK.
Thank god for LFR.