Some Irish fans were saying the same thing last weekend when Connor Murray kicked it away with less than 2 minutes on the clock.
The reality is that although its sounds easy on paper to hold onto the ball and recycle it through the phases, you are relying on not giving away a easy 3 point penalty for not releasing the ball in mauls in your own 22 or having the ball turned over. You also have less space to play with as you are effectively going backwards on each phase with keep ball tactics.
Against Scotland yesterday, Ireland had to do the same thing with keep ball but were inside the Scotland half and pulled it off, which takes off a hell of a lot of pressure.