At least I can get to use those myself as well. Probably not in every raid, but I can. And if I build an insane friendlist, I can use them myself in every raid too! In theory. I doubt whales would accept my puny event Eidolons.

But imagine to horror of Belial + Fire Beelz. At 0 Stars and only considering 1 Eidolon, that's 150% Elem attack and 50% damage boost from Berserk!