Most RFID requires near field scanners. The scanner emits an electromagnetic field that energizes an RFID device in range. The RFID device uses the scavenged power to broadcast it's ID. On receipt, the scanner must use the ID to perform a database lookup to determine what the RFID is labeling.
When you take the merchandise away from the store, there is no longer an electromagnetic field to energize the RFID. It just sits quietly. Some RFID tags are intended to be disabled by a cashier before the merchandise leaves the store. They can be disabled with strong magnets or pulsed hard with an electromagnet to destroy the device. A high power RFID reader may have a range of 15 ft. The lesser NFC devices operate in the range of a couple inches.
Another poster said similar. But will it always stay that way?