Files types are not a very sexy topic in academia. It feels like Microsoft Office has simply become ubiquitous (outside of a few Word Perfect die hards) so that everyone naturally can open any documents.
There are plenty of reasons why thinking about file types is still relevant. There are some people who, for whatever reason don’t have Microsoft Office – they may be using Open Office for example.
AcademHack does a lovely job of telling you why .rtf should be your friend.