> what's wrong with a usb-c to 3.5mm adapter

I think it just adds friction (for measure, I feel audio jacks are pretty good)

So the real response is, "what's wrong with most companies to not provide the 3.5mm itself?"

It's good that xperia's doing this though. I think I still have phones which have 3.5mm itself so there isn't much to worry about. I think there are a lot of new phones which do offer it, I think both of my parents phones have support for 3.5mm by itself.