As much as I agree generally that headphone sockets are great, there's a couple of missed disadvantages with including them in your phone: waterproofing and thickness.
> The first manufacturer to make a point of dropping the headphone jack (I believe) was not Apple – as is commonly believed – but Oppo, and back in 2014. Their reason for doing so was at least a credible technical one: they said it made their phones about half a millimetre thinner. Maybe that was a selling point, maybe it wasn’t. But Apple couldn’t fall back even on this claim, because people found ways to fit a 3.5mm jack socket into the iPhones that lacked one, and even posted videos on Youtube showing how they did it. It wasn’t easy, but it was clearly possible. If Apple genuinely thought that omitting the jack would leave more room for other features, they didn’t actually provide any.
> Some manufacturers claimed that the presence of the headphone jack made it difficult to keep their phones waterproof; but there’s a whole range of good-quality phones from around 2019-2020 that are waterproof to a reasonable degree, without sacrificing the jack.
I want the old Nexus 5 just with newer chips and camera. Indestructible poly-carbonate shell w/non-slip rubberized coating, good sized screen, headphone jack, really good battery life, no nonsense OS.
Nothing added to newer phones (Pixel or iPhone) have improved my experience, all have made them worse in various ways. Newer phones are less durable and more expensive because they are made from fragile "luxury" materials like glass. They are thinner and have crappy battery life as a result (though this is getting better as batteries have caught up to design ambition). The thinness is rendered moot by needing a case. I didn't need a case on my Nexus 5, it was already indestructible. New phone + case is definitely thicker as a result.
Actual advantages of USB-C or BT audio mostly come down to a higher quality DAC in those devices vs crap they put on a lot of phones/laptops/etc. Thing is that doesn't need to be the case, you can totally have a properly good DAC on-board. Especially if you aren't fighting for thinness and can put it on an isolated daughter board.
IMO the enemies of a good phone design are thinness and aluminium + glass construction.
It turns what should be a utilitarian device into a fashion accessory and because that is what the high-end looks like there is nothing but a sea of copycats doing the same thing but worse.
I.e. it's cost benefit analysis. It's annoying, hard, and expensive if you want to make a phone which is say waterproof to 10m or 15m while having a 3.5mm jack hole in it, which most people don't care about anyway. So easy solution, stop having the jack.