Why doesn't the World Cup use electronic technology to assist referees?

It is inevitable for referees to make mistakes, which could have been compensated by using some advanced technology, such as Hawk-Eye. But FIFA president Blatter has been strongly opposed.

The official answer is:

FIFA president Blatter has always opposed the use of video to assist in the adjudication of penalties during matches for two reasons: first, it would undermine the traditional rules of the game; second, the introduction of video to assist in the adjudication of penalties would greatly undermine the smoothness of the game; and third, it is difficult to unify the definitive judgment. He said, "Even if certain high technology is introduced but the referee is still the one who executes the game's judgment, in this case why replace the referee's duty with it? And even with video replay, the so-called experts off the field will have different views, 10 experts will have 10 different opinions."