They have user interfaces designed for completely different use cases and input devices.
Ubuntu doesn't really hide it's terminal.
Ubuntu in no way has a locked down root. A simple sudo command is all you need. In a typical Android phone, is MUCH harder to get root on.
Android and Ubuntu are much more different than you realise. From the technical details to Google's monopolistic practices. Honestly it is shorter to list what they have in common (basically the Linux kernel and a tiny selection of GNU utilities)