If the law is revised to ball out when the ball is touched, there's a reasonable chance it'll increase the number of knock-ons, as it would rush the action of the 9 (and those picking up the ball from a ruck who may have less safe hands). Endeavouring to make the game quicker by knocking off a second or two at some rucks could ultimately lead to more stoppages and scrums...
From a defender's and referee's point of view, I'd also argue it's far less clear when a ball is touched as opposed to picked up, which could muddy the waters a fair bit.