Thinking of it this way, let's imagine that this takes 2mins of your time to banner to a boss and hit it for the IS reward, so 2-3hrs to get an epic item with absolutely no skill involved at all, a child could do this.
Let's also assume that you're in an average progressive guild who can clear FT in one raid, and EE in another, and a third night gets you the ten man raid. A total of ~30 bits of loot will drop, so ignoring the time spent learning to beat the boss and wiping with no reward and assuming that all of the loot is useful (lol), let's say that nine hours of raiding for your average raider get's you 1.5 bits of loot, or roughly one bit of loot for six hours of effort, which also requires you to know your class, know the fight, practice for hours, have 19 other people turn up and do the same thing several nights a week, weeks on end.
This is why raiding offers the best rewards: it takes a commitment to turn up and organize, takes the most actual time, most effort, most skill.
But at least this option exists.