Well most productivity/office apps are Windows and OSX, and using Wine is not a really good solution.
Where are you getting those statistics from? There are plenty of productivity apps on Linux-based platforms, the repos are quite filled.
What's the difference between that and Open Office for example? (To name another open source office thing) because Open Office just doesn't work as a replacement to MS Office
LibreOffice is OpenOffice and a whole lot of patches that weren't accepted in OpenOffice. Actually it's much more than that but that is mostly what you need to know. Since OpenOffice already worked as a replacement for MS Office unlike what you claimed (it helps when you use real open formats like OpenDocument rather than OOXML), LibreOffice just does the job even better.