I primarily use a Linux machine to develop, so not having to dual boot or use a VM/Second computer every time someone sends me a .xls is very useful.
The interface mimics (older versions) of office precisely to make the learning curve for previous office users as shallow as possible.
Open Office is inferior to Microsoft Office because their mission is to be Microsoft Office, rather than to surpass it. They can never be a perfect copy.
More importantly, let's say that Open Office does try to blaze a trail to an extent that you mention. I would wager that it would probably come out like Blender, where Blender tried to make the ideal 3D creation toolkit (compared to say Maya). Blender's great! It's very powerful, it can do ALL kinds of things. However, before the v2.5 UI overhaul it was incredibly goddamn hard to learn and so it was only useful to a small section of their potential interested users.
By avoiding this, Open Office tries to cater to what people are familiar with so they can use it right after installing it. They don't have to waste time trying to adapt to a new piece of software.
Surpassing MS Office at it's own game would probably cost far more resources than Libreoffice could dream of having without having google or somebody throw a ton of money at it.
There are of course many projects that are disrupting office for certain use cases. Examples would be MediaWiki, Wordpress and google docs.
Microsoft Office for Linux did not and does not already exist.
http://www.youtube.com/watch?v=QQh56geU0X8
What is amazing is that an open source project comes anywhere close to keeping up with what is one of the flagship products of one of the largest, most profitable companies the world has ever known.
The entire mission of the Open Office suite seems to be to copy Microsoft Office as much as possible. It isn't trying to change the way people think about document editing, or provide more meaningful ways to express ideas. Microsoft created Visio, so let's go make Draw. What is the point? What value does recreating successfully developed and supported applications provide?