Actually it’s probably not what you think. I’m betting you’re thinking Apple simply wants to promote its MFI program. That’s utter nonsense since the proceeds from that program are a rounding error for Apple. They wouldn’t notice if the program went to zero revenue. They’re not changing it because there are 1.5 billion Lightning iPhones out there, many of them with Lightning accessories. There are a fraction of those iPhone users who have other Apple products, and most of those are consumers with Lightning products like AirPods or older iPads. They’re resisting changing the iPhone port because there are so many people with Lightning now. They’d get pushback except from YouTubers and tech geeks if they went USB-C. Not everybody’s in the techie crowd. Normies want Lightning because it works with what they have. If Apple sees that changing, then they’ll switch ports. They don’t change things without a compelling reason. For example, the last two Beats products came out with USB-C because they want to expand to the Android market. Hardly anyone there has anything Lightning. Note Apple branded AirPods remain Lightning.
Personally, I saw zero reason for Apple to change to USB-C on iPhones until they created the ProRes video capability of the Pro phones. With transfer speeds being affected, there now is a compelling reason to go to Thunderbolt, not USB-C. For that one reason only, they should change the port, but only for the Pros unless they expand the ability to shoot in ProRes on their non-Pro phones, which I doubt they will do since ProRes is a professional format. The non-Pros should remain Lightning for the reasons I mentioned above.
As a techie myself, I have all sorts of Lightning and USB-C items so it doesn’t bother me what ports Apple uses because I always bring one cable for all items, so I can charge everything simultaneously. At home, everything that can charges wirelessly. Whether it’s USB-C or Lightning, I have the cables and will bring one specifically for my iPhone. But the iPhone 13 Pro was the first time I ever thought Apple actually has a reason to switch.