A GSM Arena poll regarding 3.5 mm headphone jacks on phones found that 69% of those polled wouldn't consider phones without a headphone jack, 14% didn't care, 9% had switched to Bluetooth/USB-C/Lightning products, and 8% were living the dongle life.
https://www.notebookcheck.net/69-of-those-polled-wouldn-t-buy-a-phone-without-a-3-5-mm-headphone-jack.272600.0.html
Which is plain stupid. Attach dongle to your headphones and you will never notice.
On the other hand, 3.5mm-Type-C adapters may have dedicated audiochips which improve quality. Plus type-C can do active noise reduction. Plus all phones charge very fast and in 15mins of charge you get half a day of music.
The only people in trouble are iPhone users. iPhones charge slowly.
Basically people say "we love music but we don't want better quality"...which means most people are either stupid or not competent in the question.
This is not exactly correct.
First question, the usb type-c can carry analog audio through its pins, the iphone lighting connector no, it is only digital, for this reason the usb type-c can use the dac and the internal amplifier of the smartphone and the cable is a simple connection cable, on iphone this is not possible, the lighitng and only digital, dac and amplifier must necessarily be integrated into the cable.
Second question : the sound quality depends on the dac and the amplifier regardless of whether it is in the smartphone.
Third question : Not having the 3.5 jack is inconvenient, you always have to remember to have the cable with you, for example if you listen to music on good headphones and the next day you forget it at home, you can not connect any headphones to your smartphone, for this I have an iphone 7 plus, in addition to the connector in the package I bought a Fiio I1.
Then there is the problem that you can not recharge and listen to music at the same time