Or maybe more to do with users buying more of a particular brand of Bluetooth headphones and not having an arbitrary and universal input (you can do a lot of crazy stuff with an audio jack see square).
I suppose that might be one reading, though IMO the battery, jack, and card slot have just been replaced by more bells and whistles like more/fancier cameras, biometric sensors, NFC, and other gobbledygook that was more important to someone than being able to plug into the cassette adapter in my car. Not exactly what I think of when I hear "nothing left to take away."