Many western viewers prefer English voiceovers over reading English subtitles (sub), allowing them to focus entirely on the animation. English localization for adult anime requires dedicated voice-acting studios that specialize in mature content.
If you're interested in learning more about Japanese culture, astronomy, or literature, there are many free resources available online, such as: shinseki no ko to o tomari dakara dub free
(An image of the main protagonist, Eren Yeager, in his Survey Corps uniform.) Many western viewers prefer English voiceovers over reading