My question is about World Cup extra time rules, but I guess it applies to FIFA in general.
About the FIFA extra time period, the rules say the following:
It shall always consist of two periods of 15 minutes each, with an interval of five minutes at the end of normal playing time, but not between the two periods of extra time.
Moreover, the complete 30 minutes are always played. You don't win if you're ahead at the end of the first 15-minute period.
So if there is no time between the extra periods, and you don't win at the end of one of them, why aren't they simply combined into a single 30-minute period?