Soccer is an unusual sport in regard to how it is officiated. Much of officiating is based on what the players expect, and a big role of the referee is game management. Those items are much more important than certain things that are in the book. The 6-second rule was put into the book maybe 15 years ago to help the refs in game management, but all players in high-level competitions know it will not be called, except perhaps in a very rare situation where a goalkeeper refuses to release the ball when instructed at that moment to release it. If there is a major example of time-wasting the normal punishment is a yellow card to the goalkeeper.
If the referee is competent, time-wasting is no big deal anyway. Simply add extra time - maybe even excessive extra time - to offset any time-wasting. If you tell a player who just wasted 15 seconds that you are adding 30 seconds of time at the end, that player is not likely to waste time again.
There are many unwritten rules and understandings that determine much of how a game is played and officiated. Most who don't follow the game closely don't understand, but that is part of soccer tradition. Things like one-person drop balls and not ending the game in the middle of a corner kick are examples of conventions not in the rule book. Back in 1978, a British ref named Clive Thomas cost Brazil a World Cup game by blowing his whistle when time expired in the middle of a corner kick. He followed the rules perfectly - and was never given a high-level assignment again. His decision to end the game exactly when time expired still shows up on lists of the biggest reffing blunders ever. What he apparently forgot was how the game is supposed to be officiated, as opposed to the letter of the law.
