I love USB-C for charging and data and display. But it does not replace 3.5mm. Aside from the things mentioned so far in the comments here, a fundamental problem is that now headphones need DACs in them.

The engineering specification states that an analog headset shall not use a USB-C plug instead of a 3.5 mm plug. In other words, headsets with a USB-C plug should always support digital audio (and optionally the accessory mode)

https://en.wikipedia.org/wiki/USB-C#Audio_Adapter_Accessory_Mode

That increases the cost of headphones and introduces a point of failure and makes things more complicated for the end user. It’s just not worth it.

i don’t even use headphones, however I don’t like buying new things that have less features then my old things, so I keep buying phones that have both sd slot and a 3.5mm jack…
however i had to give up 2 sims + sd in my latest phone… Combined slots are such a stupid idea (1 sim + sd/2 sims)

Another reason I discovered recently. I work at home on a company laptop. Can’t do shit with it so I listen to music via my phone or personal desktop. I tried using Bluetooth gear but realised quickly that if someone called me on teams/Skype or whatever, switching device with Bluetooth is tedious and slow. Wired stuff goes out and in, boom. Oh and none of my computer’s have a usb c port despite one being fairly new (2021).

USB-C is getting standardized everywhere now

3.5 mm has been a standard from the motherfisting 1950s

It seems like you are assuming that the only device that I want to use headphones with is my phone.

I’m a musician. I’ve got tons of audio equipment I’ve accumulated over decades, most of which use a typical analog headphone jack. So if I fully switched to USB-C or Bluetooth headphones, I would need to get a powered adapter of some kind that would then digitize what likely would have been a purely analog signal up until that point, just so it can be re-converted back to analog.

Or I could have sperate headphones just for my phone. Which seems silly.

So I took the 3rd option: got a phone with a headphone jack. The Xperia still has a micro SD card too.

Also I have dabbled in soldering circuits and doing basic repairs. I can easily replace most analog jacks and repair most cables. USB C… It’s possible, and I will try to learn to work with it eventually, but it’s always going to be more annoying to work with because it has many more, smaller pins.

I haven’t seen a single phone that has more than one USB-C port, and I would like to listen to stuff while these these phones charge their miniscule batteries.

My laptop has exactly one USB-C port. It’s on the back and it’s the one port that directly connects to the GPU so slightly better performance if I use that with my external monitor. The audio jack on the side is much more convenient to use. Strike 1.

It is honestly pretty rare for me to listen to something on my phone. The rare times I do use my headphones with my phone it’s because something took out my internet while I was in a voice chat and I just unplug the headset from my laptop and plug into my phone to take my friends with me on whatever adventure it takes to investigate. Strike 2.

I already have a perfectly good headset with 3.5mm. Getting a whole new headset or even an adapter just feels like extra added cost for no real gain. Strike 3.

Bonus round. I can plug a 3.5mm headset into my Nintendo Switch while it’s docked. Can’t do that with USB-C. It’s an odd thing to mention, but I have made use of that enough times to bring up.

Bonus bonus round. I have tried giving bluetooth a chance, but every time I’m massively let down. Initially things sound fine, then the moment I connect to a voice chat it’s like I’m listening through water or something. Maybe it’s the bluetooth headsets in my price range or maybe it’s just bluetooth not being good in general but I can’t work with that. I have a hard time with my hearing. I need people to be as clear as possible and I know for sure I get that with a wired headset.