Because RFID labels are orders of magnitide more expensive than bar codes and printed labels. The groccery margins are simply to small for that. Hence the sarcastic comment of using expensive tech (that had its own hype curve in the early 2000s), to solve the how-do-I-know-whats-in-my-fridge-without-opening-it problem.
IF RFID was useful for other purposes it would be worth the small cost (scale can bring RFID costs down - it would cost more than bar codes, but potentially can bring enough logistical benefits that overall it is cheaper). However so far the logistical benefits can't be realized because you can't be 100% sure you read all the tags in a room.
Aren't RFID tags on all groceries a viable solution to make product info available to a fridge?