People are more familiar with MS Office (Microsoft Office). They don't want to change. Being reluctant to change may explain parts of the human nature. Okay, someone likes the Ribbon UI MS Office promotes. Someone doesn't like this UI but she or he becomes familiar with it.
Secondly, people expect OpenOffice / LibreOffice to be a Microsoft clone. Whatever MS Office can do, OpenOffice / LibreOffice should be able to. People expect the resulting documents to be the same. Unfortunately, it is not possible to achieve the same format because of a lot of legal issues probably only lawyers can understand.
Thirdly, insufficient advertising is available and advertising is costly. OpenOffice / LibreOffice's advertisements are not as frequent and cannot be as frequent as those of MS Office. MS Office is supported by a huge company. OpenOffice / LibreOffice is supported by donations only. OpenOffice / LibreOffice cannot afford to pay the advertising costs. Not every influential individual knows what OpenOffice / LibreOffice can do for her or him. Decision makers and government officials might not want to bear the responsibility for favouring the use of one office suite product. What would happen if people complained about the policy, for example, some technical formats not displaying consistently?
Moreover, it would take a lot of valuable time spent on training people to use OpenOffice / LibreOffice. OpenOffice / LibreOffice is not for everyone. Some people might think that they would stop training themselves. Some people tend to give up more easily than the others in using the computer software. There are situations when people rush to complete their tasks. They are in a hurry.
Not wanting to change, expecting a clone, insufficient advertising and busy people are the reasons why OpenOffice / LibreOffice doesn't win in the office suite competition.