Why do binary files contain text but text files don't contain binary?

[via Unicode]

Dear Roger,

because in when unicode is used in real life, utf8 etc then

   text ⊂ binary

John Knightley

On 2020-02-21 20:21, Costello, Roger L. via Unicode wrote:
> Hi Folks,
> 
> There are binary files and there are text files.
> 
> Binary files often contain portions that are text. For example, the
> start of Windows executable files is the text MZ.
> 
> To the best of my knowledge, text files never contain binary, i.e.,
> bytes that cannot be interpreted as characters. (Of course, text files
> may contain a text-encoding of binary, such as base64-encoded text.)
> 
> Why the asymmetry?
> 
> /Roger