I always thought that you needed some sort of inspection before checking in???

At HND, I always visited the customs desk prior to checkin my luggage. They would scan my passport after I showed them the goods I bought that are still wrapped in sealed duty-free plastic (blue strip). Then I would check in.

Since I travel with clamshell check in suitcases, it has been a hassle having to plop it on the floor to open. This last trip, I then only claimed a refund on the most expensive item I bought, so that I would only have to take out and present a small item. Although I regretted this since the sum of all the smaller items I bought ended up being more than my expensive purchase.

A long time ago, I remember showing up at a tax refund inspection counter pre-check in at Bangkok Don Mueang and the lines of open large suitcases snaked far beyond two check-in aisles. There was also a hefty "processing fee" with each transaction which also makes it quite discouraging to claim.

I do agree with the comment above that this scheme is also a money making enterprise for the government. Left hand taking from the right hand.