Because you never know when Nanto's going to drop a random Tezuka episode.
This is actually an episode I was working on several years ago, but never finished when it was announced that the series had been licensed for legal streaming in North America on the late lamented Anime Sols site. I had also subtitled the first three episodes myself, which is a shame because those were the only ones Anime Sols released, and they never got any further. Had I been able to predict the future, I would have subtitled episodes 4-6 instead.
I haven't heard any news of W3 being licensed for DVD release in North America (like Dororo was), so it's time to go ahead and release this to my people.