How is anime and manga piracy "good" for the industry?

Like I have heard that it works as "free advertising". For my case when Im watching ongoing anime 90% of them are on crunchy and rest not licensed in my region, same way there any many manga that are only available in "those" sites. So Im watching and reading these unavailable contents from "illigal" sources. Then there are those who pirate 100% of it, so how does this work?