The problem has always been this; compare the value of your two options and you'll see which is better. The anime fan community outside of Japan largely prefers the service fansub groups provide over the legal alternative. You are getting a better product, and for a better price (free).
Most anime fans want subs rather than dubs, and while people are starting to recognize this it hasn't solved all the problems. People actually trust fansub groups to give better translations than the official release versions. They don't Americanize anything and put them in a format people are used to and like (leaving certain things untranslated, karaoke intro and effects on subtitles). They also release episodes much faster, people who download are usually watching as it airs and don't want to wait extra time.
They have made progress with things like Netflix and Crunchyroll, its all about convenience and value. If its vastly over priced and there are other options, people will not buy it. If someone else is offering a similar product, but it is improved in several ways, people will want that version instead. People are willing to buy things even with piracy being an option, you just have to make it so it seems like an easy choice to just pay for it.