This question already has an answer here:
I'm looking into tax free shopping in Japan and I noticed that if I decide to buy consumables tax free then I cannot eat them on the spot. From my understanding, if I buy consumable products at these stores they will give me a sealed bag with my consumables which I have to wait until I leave the country to open it. Why can't I just open up the bag when I leave the store? What is the reason to have that tax free rule implemented?
Edit: I explained the situation more in detail to differentiate between buying from a duty free spot in the airport than tax free shops. If they work the same way let me know.