I already wrote about the topic “rooting of Android” in 2013. Since then the direction of Android itself changed a lot.
Things which where not very popular five years ago are now quite normal: films are being watched on mobile devices with services such as Netflix and games like Pokémon GO generate huge sales (by the end of 2017 about 890 million USD). For the providers of such services it is of course important that the data of the apps is not accessible by third parties – for example to protect DRM mechanisms.
Another area are payment services, such as Google Pay, which got introduced in 2015 – and again, it is important that no third party can access confidential data.