Why don't people resign?

Because blunders and miss clicks happen. I lost a recent game I was winning because I miss clicked, giving a rook away instead of putting the king in check. And I remember the game I was losing right up until they put their undefended queen next to my king. I was able to get a draw.
So yeah it's worth playing on.
The only payment option will be good. After +3, the opponent must have the option to resign or accept a $10 gambling challenge.