Firstly, the "Deciders" in the medium and large enterprises most often simply go with Microsoft's Office products. Regardless if libreoffice (and similar open source office suite offerings) provide the same functionality, these Deciders are already won over; so they simply "go with the flow". In order for there to be some sort of universal linux, there has to be an easy way to run Microsoft's Office products. That takes care of a huge number of typical office worker use-cases. (I'm leaving out surfing on the web, because that is already proven on any linux machine.)
Secondly, there is a need for native device drivers. If the Deciders can choose computers for their office workers that "just work", then their choice is easier. For this, computer manufacturers have to really help in crafting native device drivers that support linux.
I firmly believe that once the above 2 conditions are attended to, linux will then become something the Deciders can consider for the enterprise...then - with that many large numbers of users around the world - linux will have its day on the desktop.