Article for context:https://www.theverge.com/2023/9/12/23870522/iphone-15-pro-max-thread-smartphones (Ik that I am talking about multiple companies when I refer to android companies but many singular companies make more innovations in the phone space compared to apple)
I believe it was originally to do with focus, and applying "Shallow depth of field" effects, aka blurry backgrounds.
But now you can get cool features like, being able to scan things with your phone (for say 3d printing), but it's far more accurate than anything else on the market.