Recall that there are two clocks in football that keep track of time:
A team will use a timeout for one of the following reasons:
Time is such an important factor in a football game. Any extra time can mean more time to run extra plays. As a result, teams will do whatever it takes to conserve time, especially if the score is close.
Changing The Play Design
A team may decide last minute to change the play design if they see the opposing team lining up in a specific way. Calling a timeout will give them time to regroup and change strategies.
Delay Of Game Penalty
Recall that the play clock keeps track of time in between scrimmage downs and counts continuously toward zero. A team will call a timeout to prevent a delay of game penalty if they think the play clock will hit 0:00.
Icing A Player
Icing a player is a technique used to get a mental edge over the opposing team. Imagine the score is very close and there is little time remaining on the game clock. If a team calls a timeout just before the play, they may cause the opposing team to make a trivial mistake costing them the game.