I don't get whats weird about that? You need some kind of device in order to listen to Spotify and today there is a lot of services competing with Spotify.
Spotify also have a huge number of free accounts that rely on ads which probably means less profits for Spotify. Everyone still needs to actually spend money to get the device but you don't really need to spend money to listen to music. Also, while Airpods is a "one off" purchase, a lot of people don't like having subscriptions (like me for example).
I have spent hundreds of dollars the last years on headphones (not Airpods tho) but I hesitate for a long time before starting a subscription service. Not because I cannot afford to, I just do not like subscription services.
Spotify, Youtube Music etc provide a free service. With adblocker, music.youtube.com is totally free without any ads so I have a really hard time to justify the cost of another paid service like Spotify.
Edit: if you downvote this, please comment on why? What is incorrect about my statements?