When it was suggested to British PM Winston Churchill that spending on the arts be cut to help fund the war effort, he reportedly said: "Then what are we fighting for?" In fact, he didn't. You only need to see one of his paintings to know how far-fetched that is. And can you really imagine the old warmonger parting with a shilling that he could have put towards killing more people? But that doesn't make the point any less salient.
Any time money is used for something that is not, on the face of it, "worthy", according to the definition of worth prevailing at the time, then it's easy to argue against it by saying: "Why isn't that money going to fix child poverty/public transport/homelessness?"
The answer is simply that money needs to be spread around to make life worth living. We need our surroundings to be places those children can enjoy, where there are things worth taking a bus to see and in which you would want to have a home.
But when money is to be spent on art not of the conservatively bilious variety, public opinion is easily persuaded that maybe we should use that money to do some good. As if it's not good to have beautiful surroundings.
Public submissions are now open regarding Michael Parekowhai's Lighthouse to be sited on Queens Wharf - the existing wharf, not an extension that will take up more harbour to accommodate it. Most of the cost is covered by private donations.