Players, parents, and coaches often complain that the ball had clearly crossed the touchline or goal line, especially for a throw-in.
There are two key reasons for this:
First, many players and parents (and even some coaches) don’t understand that for a goal to be scored the entire ball has to cross the entire goal line. The same applies to corner kicks and throw-ins. If even just a fraction of the ball hasn’t crossed the line then we play on.
Second, parents and coaches simply don’t have nearly as good a viewing angle on the lines and proximity to the ball as the Assistant Referees that are looking directly along the lines. If your viewing angle is off by just a few degrees (sitting in a chair three to five yards back from the touchline) you can easily convince yourself that the Assistant Referee made a mistake.
But please realize that you are almost certainly wrong.
The image above shows a perfect example from a very recent game between West Ham and Chelsea in the English Premier League when a West Ham defender cleared a Chelsea shot off the goal line.
The league recently introduced goal-line technology that captures and analyses video of the goal mouth action and then sends a goal/no-goal signal to the referee.
The above image captured by this technology shows that the ball did not completely cross the line (the goal is to the right of the ball) and therefore no goal was awarded.
Btw, even the Assistant Referee standing ~25 yards away at the corner flag probably mistakenly would have signaled for a goal. Imagine parents and coaches trying to call this accurately from the touchlines!
So for the good of the game please realize that the referees are in the best position to get this decision right. It won’t be perfect because we don’t have this goal-line technology available to us, of course, but odds are high that the referees will be much more accurate than parents and coaches.