It is important when trying to anticipate and react to the actions of other drivers, because, as stated "a majority (emphasize added) do not [completely stop] at the stop sign", which will put all other drivers at risk. So even if you follow all the rules and go when it is your turn, you are still at risk of being in a car crash. Therefore, anticipating other drivers and looking at what they are doing ahead of time is needed, and reaction will be needed if they do not follow the rules.
hope this helps
