Supermarket TV Ads Screen with IR Sensor

Used to be, the commercials or info ads were running all day, all night unless attended to by a supermarket stuff. A waste of electricity and LCD screen/dvd player life. Now, they are using what could be an infrared sensor that detects movements/shoppers, it only plays when there is actually one soul to view the ad. The IR sensor is cheap, the money saved from electricity savings will cover the IR sensor many time over. The only question is, why only now?