One feature, one I consider genuinely useful, that digitally connected headphones (be it Bluetooth, Lightning, or USB-C), in a tightly controlled ecosystem like apple’s, is headphone volume safety. When using digitally-connected Apple-made headphones, iOS can carefully monitor the actual headphone output, optionally limiting to an actual volume output, and not just a “dumb” maximum setting that’s unaware of the sensitive of the headphones in use. With compatible headphones, you can view real-time output (see attached screenshot from my iPhone). You can optionally configure it to limit to a particular dB level, and again it’s based on actual content volume. So if you need to turn the volume way up for a quiet recording, you still can, and if you forget to turn it back down for a “hot” recording, it will protect your ears.
(Way better than the old EU volume limit, which has no way of knowing what headphones were in use, and so by law the limit was based on the included headphones, often leaving you with insufficient volume with headphones.)
What I don’t know is whether Apple has a mechanism to allow third-party Made for iPhone headphones with digital connections to work with this system. If they don’t, I hope they enable it eventually.