Because there’s nobody in the LFG system, because nobody cares or plays on that realm.
Now just remove this stupid artificial MP requirement - if anything it’s only for the doors/passages. It’s not helping the case of D4 at all, since as a dev and game operator you can’t gurantee the existence of a healthy group community across all realms, and especially so in a game that’s to be played solo as a primary activity - this is not WOW, you’re not dealing with the same players: there is no 5 man and no 25 man extensive content and you won’t create a comunity for it with just 1 event.
Also, if that’s just aspirational content, why is it part of the main quest end? At least put it on the side like the tempering tutorial - and provide another means to get that currency.