The game is one of attrition, possession, and field position. By taking away the penalty you take away the option for guaranteed points, and for territorial advantage.
To retort that the referees still have the ability to penalise is really odd when the argument to implement is that 'refs don't penalise'.
This was trialled in an All Star game where the coaches didn't bother to think about how to exploit it because it means nothing, but in the NRL it will be targeted.
This is definitely not the season to trial some of these things - there is a potential to be one of few sports in the world that will be televised. So instead of promoting the game, we are going to turn it into a slow, sluggish, and confusing sport to watch.