then if you did that the team winning would run out the clock which would be boring to watch.
The extra time is what is exciting as you never know if say Portugal might grab a goal, plus they d tell you near the 3nd of the game how long is left and 99 times out of a 1000 the ref calls it on that.
Look at NFL, the players and team know when the end of the game is so many teams winning just stop playing or the losing team knows they can’t win and give up which is extremely boring
It’s all a matter of point margin in any sport, and soccer would be no different. If there’s a minute left and you’re down 1 score, then you’ll work hard to even the score.
If you’re down by 4 scores, then it will be different.