iPhones have supported hardware encryption for over 5 years. Android phones... well, it's complicated.
When Google announced Android Lollipop, one of the most important features for customers in the post-Edward Snowden era was hardware encryption enabled by default. Put simply, on first-boot your personal data would be kept far safer on your personal device. Unfortunately, it looks like default hardware encryption in Lollipop is a nice-to-have, not a must-have, and many Android phone vendors have simply decided to keep it off.