The phone comes with an adapter.
One way to use headphones with your phone is to have a pair of earbuds that you carry around. The adapter stays attached to the earbuds and there's no real difference in quality of life.
Another way is to have headphones at different locations: home and office. Having to buy an extra $9 adapter or two is not a big deal, relative to the price of other equipment.
Often there is a pair of headphones that we want to use with either the phone or some other pieces of equipment. You can use a little piece of thread to tie the adapter to the end of the headphone cable so you don't lose it.
This does not mean the lack of a headphone jack isn't stupid.
(posted September 7 '16)