Nobody really gives a shit about Singapore. Too bad.
Think profit wise. Metal in Singapore? It's sad as hell. All the effort, all the blood and the sweat, it all amounts to what? A small show that makes everyone in the show happy. Big deal, the profit doesn't multiply based on how happy everyone is. So what's the point? I've already given up on even hoping to see big metal acts play here.
Then let's think from the perspective of the band, as someone said above. Censorship, why should I come all the way to some tiny little island just to be told what to do? Who cares about PR here? The fanbase is just so small that it's expendable. I've given up hope on metal in Singapore. You want metal, you take yourselves out of here. Impiety style.