Weight in the lobby
Lobby groups may be obstructionist and hopelessly at loggerheads, but they are a crucial part of any good democracy. It helps for an organisation to have pooled all its time and resources into one issue, no matter how offbeat or inane.
This is both the strength of the Greens and their weakness. There is broad agreement for their cause, even causes, but this does not translate to larger numbers of first preference votes.
And the kind of organisation that represents pedestrians or public transport advocates has a full-time putting forward their position. They need no greater power than the sympathetic ear of a sitting member.