You're missing a major point of why so many people pirate anime; lack of legal access to IP. The majority of anime created wouldn't be seen by Western watchers if it wasn't for such piracy sites. This is usually because of licencing (more likely the lack of) making it impossible for people to stream or purchase a series/season legally.

Take SAO, AllTheAnime we're the only company to get a publishing licence in the UK. If it wasn't for AtA, we wouldn't legally be able to view the series on any any platform here. Physical disks can also be prohibitively expensive.

Another point is affordability; so many of people's favourite shows are spread between multiple different streaming services and with all the services regularly upping the cost per month, the price of entry to watch an anime, especially with there now only be 1 truly specialised service, is extremely expensive