Except there's a cycle - you get 3% back on Apple purchases. Notice I said "free" with air quotes - sure, you are spending money, but you are also being rewarded for staying in the Apple walled garden. So back to my point - why pay $9-$15/mo for Spotify when if you play the game, Apple has a "good enough" product and is incentivizing you monetarily to the point that their services become "included" rather than a separate line item in your monthly budget. Maybe it doesn't matter to you, but to a wide swath in middle America it does.
Exactly.
You can use CASH back for any further credit card purchase, including a Spotify subscription for that matter. Wouldn't call Spotify "free" though.