Maybe they don't want to spend $400 for specialty headphones that pretty much only work with the iPhone.

Because wireless headphones work with all BT devices and cost hundreds of dollars less.

They are also convenient to use while commuting and while working out, which is basically 95% of my time using headphones with my phone. Ambient noise while walking, riding a bus, or being in a gym is generally too noisy to prioritize audio fidelity anyway. That's not what listening to music on my portable phone is for. I have better headphones for my desk.