They also have the best interface, loads of curated playlists, and algorithms that actually serve up music a listener is likely to appreciate. Since they added podcasts and books, it makes it even more of a one-stop app/service for most customers' audio-focused entertainment.
And with features like sharing playlists and Spotify Wrapped, they really reinforce the social and community nature of music, and staying with their service in particular.
¯\_(ツ)_/¯
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