Android is Google tech tht happens to use the linux kernel and that's it.

All the other stuff you expect from Linux distros and GPL/GNU/Open-source software just does not exist on android.

As a result porting existing linux-based software is impossible without the other supporting bits like the glibc libraries and the xorg libraries.

However, a chroot version of ubuntu is in the pipline for android - similar to easy debian which will give you more options.
(This is the bit I'm waiting for when I get a new device. Also bluetooth keyboards and mice or not supported in android)