Better Quality Pictures in General
You can equate the smartphone camera sphere to a sort of “arms race” among manufacturers. Every OEM wants to have the best smartphone camera on the market.
Among the more “routine” improvements that a triple-lens camera is able to bring is a general upgrade to photo quality. That’s because more sensors mean that a particular camera is able to draw in more light and color data.
So yes, it’s not that exciting of an improvement. But it’s still an upgrade over past iPhones — and it’ll help keep Apple’s devices competitive and up-to-date in a rapidly progressing and saturating market.