iPhone cameras have evolved over the years both to (mostly) improve them, as well as in competitive response to improvements in cameras in non-Apple smartphones. If there had been no such competition, maybe Apple wouldn't always be tinkering with their design, but that's hard to say, given that there have always things about iPhone cameras that can stand improvement even for average photographers. Saying that the current quality of iPhone cameras is overkill for any normal use case is kind of like saying if they're more than good enough for what you use them for, and for what you think most other people use them, then they're better than they need to be, so they should be able to use lower-quality, thinner optics to get rid of the camera bump, but that's not entirely evidence-based but rather a perception. Even if it were true, then downgrading the iPhone camera system just to make it thin enough to eliminate the camera bump would alienate that 10% of users you claim are the only ones who benefit from a thicker, better camera system, and that's not a small number. Fewer than that want Apple to bring back the iPhone mini, and in these forums they're pretty vocal.
There are always complaints about even the best of today's smartphone cameras--still not enough sensitivity to low levels of light, noise (especially at low light levels), optical zoom level, stabilization, etc.--that can make many photos less than what they could be, so Apple is aiming to make iPhone cameras come ever-closer to "real" cameras to address these complaints, and of course to snag some of the people who otherwise choose an SLR and an Android phone. The physics of current commercial optical hardware is such that to improve on some of these factors, thicker camera assemblies are needed. If that weren't true, then the manufacturers of other smartphones would have cameras as thick, or thin, as iPhones, and no camera bump, but those don't seem to exist.
We don't know how close Apple (or any other manufacturer) will get to something resembling true SLR quality, but with today's commercial optics, to get a smartphone with a camera that's able to achieve better photos and videos, apparently requires a thicker camera assembly. But at some point in the near future, metalenses as well as Samsung's ALoP technology (All Lenses on Prism, which reduces the thickness of telephoto camera modules) are anticipated to help greatly reduce or get rid of the camera bump. Don't know when that will happen, but Samsung demonstrated ALoP at CES 2025, and they're anticipated to release their first phone using it, the Galaxy S25 Slim, maybe some time around May 2025, after their 2025 lineup is announced tomorrow (Wednesday Jan 22). Don't know when or if Samsung will make lens assemblies for Apple using ALoP, or license the technology to Apple and/or others who actually make the lens assemblies for iPhones (not currently Samsung), but we'll find out as time goes by.
