It allows for machine vision and heavy maths to be executed very fast. There is basically nothing similar in an embedded format in the market. The remainder would be SoCs for Android phones (Samsung Exynos?).
Thsese SoCs have lots of hacky drivers and mostly support Android, which is not a very good fit for real time and high customization required for drones and self driving cars (AOSP build system, a google class piece of crap).
What are they using?