Piracy is not about availability; it is about convenience.

Signing up to different services that are based around monthly fees and then having to deal with those services when you might only want to binge one show is inconvenient.

Having to deal with personal data loss / fraud when those services get hacked is onconvenoent

Having to use multiple different apps (or even devices) for different shows is inconvenient.

Having to be online to watch the show is inconvenient.

Pirating can be more convenient than the above (see other posters fully automated setup) and when it is, the path of least resistance wins.