Piracy hurts all kinds of industries from music, movies, books, anime, gaming, and others. The more piracy takes away from artists the less likely artists will be to stick with it. When artists can not afford to pay their bills because their work is being stolen, they might be forced to give it up. We then lose out on potentially great artists. The good news for anime is that many people still like to have hard copies of the art, which cannot be pirated online.
Also, as streaming services become more popular, piracy of all kinds is decreasing. With less music pirates out there more resources are available to go after pirates of anime and other art forms.