There certainly is some element of fashion, especially on budget devices.

Goes like:

Premium device adds huge lenses for photo quality -> Public perception becomes that huge lenses are indicative of quality -> Imitator brands add large glass circles over lenses that don't need them to make them look more premium

And the perception is also that more lenses is better (which is true to a point) so we're getting phones with five or six cameras or sensors on the back looking like spider eyes staring at you.

If tech suddenly appeared tomorrow which enabled as-good quality with only a single small lens, manufacturers would struggle to shift back to it because the public would think "It must be rubbish"