As a POC, some have. Here's Peter McKinnon [1], and Tomorrow's filmmakers [2]. The wedding is also a very controlled lighting scenario, allowing the dedicated camera to maximize its advantage. Shutter-speed matters too, which Phones have closed in on but not yet eliminated. (In my post, I called out brightly lit conditions.)
Large camera bodies are also about looking "professional". Like most people don't wanna go to banks where staff is dressed in t-shirts and shorts.
[1]: https://youtu.be/yLZJS2k2V4k [2]: https://youtu.be/6RAVCzd0MZw