A short story.
There was one mmo where leveling was very slow (1 year to cap) so people would run the same dungeon for months before they can move to another. My time playing there was great because mostly any team i joined was well experienced and geared, so it was a friendly and easy run.
But one day publisher decided to make x3 exp rate (forever), as a result most of dungeons became swarmed with new people who had no clue what to do and of course 4 of 5 teams would disband due to continuous wipes. Needless to say people stopped joining public teams - only friend list teams and statics.
End of the real story i have been through.

I think doing hard content in a casual game is pointless (except for elite players who move with their static). 95% players are very bad and will never improve because they don't have to work for gear and level.
Someone gets lv50 in 2 weeks and in 2 more weeks he is full i90 and ready to join any coil/ex team with very little experience of doing endgame content or even playing their class.