You can take RAW photos with your iPhone, you just can't do it with the default Camera app. Apple does allow third-party apps to access the hardware and software needed to take RAW photos, so you can use one of the many options to do it. RAW photos provide a lot more flexibility than HEIC or JPEG photos, but with a much larger file size. Using a third-party app means you can keep using the Camera app for regular photos and use the other app when you want to take RAW.
You can also watch this video at YouTube (but with ads).
Link: Apple’s List of Raw Photography Apps.
Thanks Gary. I downloaded the ProCamera app awhile ago and hadn't realized I could take RAW photos. Really need to learn this app. There's a great deal it can do.