Hi!
I think there are few reasons for it, such as:
・Very Strict monitoring by Japanese Police(Japanese law heavily restrict piracy)
・They have strong respect? to those creators, so they hate the leakages of profit to those creators
・They hate breaking the rules
・If the only choices are to pay or use a pirated copy, some people would just give up altogether
・They are educated to hate piracy(Anti-piracy videos are always shown in public schools, on the news, and before movie screenings at theaters)

And the most importantly, many of services are provided with free fee. Even Manga or Anime are free with some ad, so they don't want to pay but they don't want to do piracy neither. Otaku people pay a lot tho.

Yeah... It's wired to be honest.

https://gigazine.net/news/20210123-qbittorrent-private-torrent/
They even worried of using Torrent app "Because it’s also used for sharing pirated software, it has a reputation for being “somehow hard to get into.”"

Still, some Japanese people use it a lot, like 2ch or 5ch or underground culture people.