Headline features get the attention, but major iOS updates typically rework core frameworks — memory management, background task scheduling and security sandboxing — that affect every app on the device, not just Apple’s own.
Developers usually get these frameworks months earlier through beta releases, which is why some third-party apps feel noticeably faster or more stable right after a major update while others lag behind until updated.
Security patches bundled into these releases are often the most important part for everyday users, even though they rarely appear in the marketing highlights.