Why Spotify has no button to filter out AI music

For the same reason Facebook, Instagram etc accept AI-generated videos. All they care about is how much time you waste on their platform.

Spotify is a bad actor in many ways, use other services for music.

If a headline asks why, then the answer is money.

Spoiler: they want as much money as possible.

because that's bad for the algorithmic slop pipeline that costs them way less than paying real artists