Most businesses do not care, because it's harder to counter bots when allowing overseas traffic. Moreover, the number of Japanese who leave the country are a small fraction. For reference, the percentage of Japanese who hold a passport is 17%. A small fraction of the 17% represent students studying abroad (or other long-term stays).

There's enough internal demand that people travelling abroad (or studying abroad) are considered edge cases worth ignoring. As surreal as this sounds, this is the current situation.