It's too expensive in terms of resources
"When WildStar announced that it was scaling its biggest raid down from 40 people to 20, commenter Belladonna did some math. The short version is that every single person who was playing the raid in its 40-person incarnation had personally cost $2,500 based on a handful of reasonable assumptions, which would require fourteen straight years of subscribing for Carbine to even break even on the money that the raid cost to develop. It's sort of a weak investment."
It's designed for a tiny portion of the people playing the games
"Why did Turbine stop designing raids for Lord of the Rings Online? Because no one played them. And that isn't a recent development, either. Sure, maybe Lord of the Rings Online is unique in that regard, but it sure doesn't seem like it.
There are plenty of data to be unpacked in this post when it comes to raiding in World of Warcraft, some of it outdated, but at the height of the game's popularity (Wrath of the Lich King), it still makes a pretty clear argument that raiders made up about 10% of the population: About 1.1 million players were killing the first boss of the highest tier of raids available while the game's overall populace was upwards of 11 million."
It's a little dated, and I don't see six reasons, but it does bring up some interesting points. What do you think of this? What would the alternative be if there is any?
Personally I've always wondered what people that don't raid or PvP do in the game.