They are for the ones whose phone is so old that the latest iOS stopped supporting it.
Think about the amazing leap you get from an iPhone 6 to iPhone 13? That's not "iterative", it's damn revolutionary.
I'll be forced to update when enough apps (not Apple, but third party) stop working because they no longer support iOS 12. Currently, there are only 7 apps out of over 200 that I have installed that don't support iOS 12. So I have to run an older version of these apps. Eventually there will be many. And the older versions of the apps will eventually stop working as well (if they connect to some web APIs that will be deprecated). This is what forced me to upgrade from iPhone 3GS to iPhone 6 last time.
iPhone 6 had headphone connector, reasonable size and touchid. It had headphones and charger bundled in, for $650 at launch.
iPhone 13 definitely has better camera, display and performance, and it is bit more water resistant and has wireless charging. But it's larger, missing headphone connector, it has faceid (which never works in pandemic world due to masks), has no headphones or charger in the box, and cost $1000 at launch.
So there definitely are improvements (the quality of life from wireless charging, nicer screen and camera) but it comes at almost twice the cost and a lot of stupid choices like faceid. For people not interested in performance and camera, the iPhone 13 can almost seem worse.
I've got so fucking many wired Apple headphones and chargers I don't know what to do with them all.
I'm glad they're not bundling them any more. I use an Anker charger and cable anyway.
After that you just won't care and barely notice it.