Apple recently wrapped up its WWDC where it showcased what it has planned for iOS 18, which is expected to release later this year.
Since the presentation, Apple has been under fire from its customers after its announcement about Apple Intelligence, Apple's foray into the emerging technology, seemingly being integrated into every facet of technology, would only be accessible to users that purchased its latest generation iPhone. As for Mac's, Apple made Intelligence available to M1-powered devices and above. However, the only iPhone's compatible with the new technology are the iPhone 15 Pro models, not even the standard iPhone 15.
There are a few reasons for gatekeeping, and Apple customers were quick to accuse the company of gatekeeping Apple Intelligence as a scheme to drive more sales of its soon-to-be-released new generation of products, specifically the iPhone 16 line. Apple said its new AI-powered feature requires a powerful NPU and substantial RAM capacity. The only two iPhones that meet the required specifications are the iPhone 15 Pro models.
"So these models, when you run them at run times, it's called inference, and the inference of large language models is incredibly computationally expensive. And so it's a combination of bandwidth in the device, it's the size of the Apple Neural Engine, it's the oomph in the device to actually do these models fast enough to be useful. You could, in theory, run these models on a very old device, but it would be so slow that it would not be useful," said Apple's head of machine learning and AI, John Giannandrea

On a hardware level, the A16 Bionic chip found in the standard iPhone 15 models has an NPU that's twice as slow as the A17 Pro chip found in the iPhone 15 Pro and iPhone 15 Pro Max.