While i’ve been lucky enough to not ever damage my iPhone some people are not so lucky and accidents do happen. iPhones get dropped, screens smash or crack, chips are taken out of the iPhone or worse … being dropped in the pool or sink etc.
In the past you’ll take your iPhone to Apple and they’ll fix your iPhone (by usually replacing it with a refurbished model) with a fee. That fee is usually over $200-$300 depending on the iPhone model. Still a fair service when you think about it … you’re getting a brand new replacement iPhone less than the cost of a new one.