As a subscriber to this sub-reddit, the constant spamming of stories relating to people of particular ethnicities committing crimes was annoying. It became a constant drum to summon to action racist trolls and idiots.
That and it was attracting a ton of undesirables to the sub that don't even live in Melbourne. It's been immeasurably better since that rule was introduced. There is plenty of other places for that sort of thing already.