Baby bonus are particularly good for people like Keysar Trad who has no other thing to do than have 9 children, live off government grants and bash Australians at every opportunity.
I guess theoretically they could but experience has shown that unions fare less well in a deregulated labour market. Hong Kong in it's libertarian hey day had little union activity and the more deregulated a state's labour market in the US the less union activity. There's a reason unions like highly regulated work places.