https://www.cnet.com/news/galaxy-s10-shows-that-triple-rear-camera-phones-will-be-everywhere/

It was just last year when I noticed that phone-makers were adding cameras to phones the way companies added blades to shaving razors, and at this point you may be wondering why this is happening in the first place.

There are several benefits to having three cameras on the back. The primary reason is the ability to switch between different focal lengths quickly. It is similar to a three-lens turret on an old Bolex camera that allowed you to change lenses simply by rotating the turret.