File transfer that just works.
My mum can use airdrop. She sends us things. She doesn't need to install anything or configure things. She just uses the first-party UI.
It's the same with Airpods. Bluetooth headphones? Yeah, you can buy some for $20, who needs Apple ones? Apparently everyone. Turns out providing great noise cancellation and bluetooth that just works means the product is appealing to general consumers.