A real chessplayer never cares about the "!" sign . 
Cheaters care. The cheaters know that how to avoid the mark "!". Most cheaters dont have the mark "!". 
If they got the "!" they can easily pass away. 
This is the biggest problem on this chess site. 
As long as the cheaters dont have the mark there is no way to play chess. 

 I have two questions: 
1. Why do the cheaters not have the mark?? 

A tons of cheater did not get "!" mark. Why? 
WE all see them. We always know ( during the chessgame), which is sad and annoying. They are laughing like idiots, when winning A GAME, but making really strong moves. Some of them only have 100 or 200 points rating, but their moves are smashing. 
But they dont have the mark.  

2. Why the sign dissappears? 

If a cheater got the mark "!" he plays some dumb moves in the next game. The mark will simply dissapear. ( I guess)