There used to be a scrum that were contested in the sense the ball had to be fed down the middle of the tunnel between the the two sets of forwards. The hookers dangled from the front row ready to strike as the ball left the halfback's hands. All sorts of gamesmanship was involved.
It slowed the game down to the point it was a blight on the action packed game that it was supposed to be. The rule makers stepped in and effectively turned the scrum into a means of restarting the game but nothing more. It does take twelve players out of action for a brief time, which on occasions helps the side that wins the ball from the scrum.
Rules of sport are like tax laws. They have to keep changing to clamp down on those who want work outside the spirit of the law. It's to stop people who want on unfair advantage for their own benefit and don't care about the overall good compliance with said laws brings.