DAC have been more than good enough since the maturation of mp3 players in the early 2000s. The smartphone has a DAC and amplifier for its various speakers already. Heck the computer inside usb-pd power converter in the phone is many times more hardware and work and EMI constraints to respect than a DAC + amplifier for a headphone output.

The DACs/amps you linked are bigger than the Sony mp3 player I had in 2004. It had two jacks and a user replaceable battery. And it was water resistant.

I could go on and on.