1. Because you're broke?
2. Because it's the most convenient way to watch anime?
3. Because legal streaming sites sell your data and that's creepy (See the Kroll class action settlement)?
4. Because there are no legal options to watch your favorite shows in your country?
5. Because **** the streaming companies that revoke your license to the content you paid for due to corporate shenanigans beyond your control?
6. Are you an anti-DRM extremist?
7. You just like free ****, even if you can afford to pay?
8. Some other reason I haven't listed here?

For me, it's a combination of 2, 3, and 5, and 6. I'm happy to pay because I can afford to. I don't pirate stuff because I want free ****, per se. I don't judge people who do, though. I do it because I want to OWN what I paid for. I would gladly subscribe to a legal streaming service if they let me download high quality, DRM-free copies of everything I watched, and wouldn't region-lock content.

Every season, I actually earmark two or three shows to buy on bluray. I'm not perfect but I usually follow through when the bluray eventually comes out. It feels good to support the creators and get your favorite shows in full bluray quality. And there's no way for the streaming companies to (R)etroactively (A)mended (P)urchase (E)xperience you and remotely disable the blurays you bought like they can for digital purchases.

**** streaming companies.