The actual rule is not in the Rule Book as a set rule. It is usually applied by the governing Rules Committee of that tournament as a Local Rule. Much like the "One Ball" rule is invoked by the rules committee. The one ball rule only specifies that you finish the hole with the ball you start with, or if you lose it, one of the same make. Now, the PGA Tour has guidelines that all of their tournaments enforce that sometimes differ from the USGA, R&A, European Tour and on and on.
It wasn't that long ago that the Captains and Governing Committe of the Ryder Cup decided to disallow practicing after a hole. Not sure what year that was.
Pace of play does factor into the reasoning as to why such a rule would be invoked, but the best answer is that the Match is between that set group of players. They all finish the hole at the same time, so it is not to their advantage to practice over any other group on the course. Each participant in the group as the same opportunity to practice.