Lasers are everywhere today. They read DVDs, perform surgery, and get swung around by dueling Jedi. But in 1969, the laser was still relatively new technology. Many people saw a laser for the very first time in Goldfinger, and lasers' destructive power was burned into people's brains in the same way this particular laser almost burns itself into Bond's groin.
Not only is the laser used to torture Bond, but it also reappears at the end of the film to literally cut into Fort Knox's steel vault door like a hot knife through a butter sculpture. The filmmakers couldn't let this killer special effect be used in only one scene. They had to get their money's worth.
Bond films are known for their technology, but in this case it's the villain's technology that proved to be one that crossed over into the mainstream. Now, if Goldfinger had only patented the laser, he would be a wealthy man without the need for all that criminal activity.