Scrum tactics have changed so much over the years.
The full 8 man shove used to be a one off tactic for when you were on your 5 metre line or attacking on the oppositions. The hooker used to drop his hand or signal to the Scrum Half when he wanted the ball in so you had the advantage of knowing when the ball was coming in to get the shove on, the defending openside would call the ball in so his front 5 would know when to shove.
Now it's, lean, feed, try and get the penalty, fold. It's actually a suprise to most people when there is quick ball from a Scrum.
It's actually a bit better than it was about 5 or 10 years ago when there were serious calls to get rid of the Scrum altogether given how much of a time wasting eyesore it had become. I think props realised if they carried on with the self-indulgence they would soon find themselves out of a job.
Interestingly the above only really shows in pro rugby in the UK. At grass roots the Scrum is still a good contest that doesn't get away from its true purpose that is to restart the game.