[pjmlp]

Because Linux is not exposed to userspace.

All you have access to are Java, Kotlin, ISO C, ISO C++, and NDK libraries.

Nothing about Linux is public, other than APIs used by OEMs themselves.

Since Android 8, even Linux kernel drivers are considered legacy and all new ones are required to be Treble based.

All the LinuxSE, seccomp,...are also not exposed and can only be customised by OEMs.

People like to pat themselves on the back regarding Android, however it could start using any other kernel and the apps sold on official stores would at most need to be recompiled.