As the title says. The reason for this being that too often, for raid groups especially, the group leaders asks for a (ridiculously) high item level while not having that themselves. Sure, you can optionally enter a minimum item level which you cannot set higher than your own. And that's a good thing. I personally prefer groups that have this, so I know the group leader isn't simply organising a run in order to be carried.
That in itself isn't an offence, of course. People choose to participate in such runs willingly. But this is often under the pretence that the leader is of the same level that they are asking, which is too often not the case. I guess my biggest point would be to have this as a way of preventing 'false advertising'. So people can make informed decisions when signing up for a group.
Sure, we'll still have those "I'm an alt of a Mythic 5/8 raider" people and with the Legiondaries gone, I hope that people will realise that asking the same item level as the drops you're going for isn't feasible anymore, but regardless I think that this simple change would do a lot of good.