Bottom line: Insurance.
To be fair, I never thought I'd use AppleCare. I'm careful with my phones. Bought it on my first iPhone. Turned out my NFC chip was proven defective over a year later. Bonus: New phone with a new battery.
How could Apple predict that on a scale i wonder ... You can only based that only by the number of repair have come in before you can come to that conclusion,Typically they live a rougher life and need more repairs. Thus the warranty is more expensive.