So this comment made me go looking, and there _is_ a case that adds headphone jacks back to iphones, but literally not a single one for any model of android phone. I guess they figure that the people who care enough to buy such a case will go out and buy one of the dwindling number of android phones that still have such a jack.
Apple devices have a much smaller variance in shape. It’s a lot easier for case designers to develop for Apple. Android devices have a lot of variety.
That said, I have seen some fairly cool cases for Android devices, so I assume that some case companies support just the big sellers.
The divide generally is that android phones with headphone jacks as of 2025 generally dont have 5G ultrawideband support* . And there are some split-out dangles which offer a jack and usb-c, but they've sorta had annoying quirks in my experience (the CableCreation one is less terrible in my experience). One could design a case around one of these dangles, though it's add some bulk and the dangle quirks mean you sometimes need to disconnect it from the phone.
* - supposedly the Sony xperia pro (2020) might be the rare exception to this rule.
The don't always seem to work either. My wife asked for one of the little USB-C to 3.5mm adapters of which I had a few from various Android phones over the years, and one from an iPhone and she couldn't get them to work on her Samsung Galaxy S21, I ended up buying hear some bluetooth earbuds (yes, she could have done it herself but she trusts my judgement on selecting these sorts of things).
This is probably as much of a reflection of the market size and lack of device fragmentation for the apple ecosystem than demand.
It's similarly easier to buy a wide range of different case designs for apple.