It’s an interesting question. For one, I know that the Photos app on Macs and iPhones tends to spend loads of time going through your photos and recognizing everyone’s faces. Due to Apple’s stance on privacy, they’ve emphasized that this task should be performed on device, not in the cloud.

Without the neural engine, the processing of tens of thousands of photos can be a real burden on a typical MacBook. Apple has tried to throttle the process so that it doesn’t peg the CPU, but then it takes a lot longer to complete. The neural engine lets the process run full out without consuming a ton of power.