iOS has had a ton of effort put into its audio stack - it was an iPod replacement as well as a phone. Remember when the app was still called iPod?
iPod users wouldn't have taken the iPhone as seriously if Apple hadn't put in the work to make audio a first-class citizen. Android doesn't have that pedigree/baggage so it's never been as important.
e.g. lots of Android phones basically can't hit low latency audio targets that iOS has been able to hit essentially since launch.