As a referee and referee instructor, I understand that some referees do not set the bar for calling fouls and misconduct appropriate to the age and skill of the players, and the temperature of the match. In instructing referees, we talk about the need to call unfair physical conduct because it is important to keep the player's safe (our #1 priority) and because the failure to do so can result in a loss of game control by the referee. Particularly with teenage players and school rivalries, loss of control can lead to a brawl.
That said, the notion that everything needs to be called, while commonly held among fans, is one that is contrary to the traditions and rules of soccer (and perhaps all sports). I talk to a lot of coaches about this issue. While few complain that referees are calling too many fouls; most complain when trifling fouls are called against their team. Most strenuously complain when a goal scoring opportunity is taken away from their team because the referee stopped play rather than awarding the advantage under Law (NFHS rule) 5. Particularly during playoff games, skilled players can, and want to, play through fouls and contact as they are able to continue the attack.
But, that also doesn't mean that such contact should be ignored by the referees. Fans (particularly from the stands) may not notice the referee speaking to the players (both victim and perpetrator) about the conduct. Private and public warnings are important to match control even if play continues. The referee also needs to constantly monitor the reaction of the players and the conditions of the match. What the players may tolerate once, can lead to frustration and retaliation if repeated. Many boys will be vocal when that point has been reached. Some girls react differently, and the referee must look for other clues (such as a hard glare).
I once did an adult match in which the players no longer wanted to play and were so frustrated that they were mostly involved in hard contact with each other. In response, I blew the whistle for everything the laws permitted. I required the restart to be at the exact blade of grass where the foul was committed. The flow of the game ground to a complete halt. The game ended ten minutes later without any added time. It was no fun for anyone, and there was little "play" during that ten minutes because of my constant whistling. But it was, IMO, necessary to prevent bedlam. The experience taught me, however, the wisdom of the notion, now again expressly in the laws of the game, that the referee must call the game consistent with the spirit of the game, not just the letter of the laws.
