Categorizing and Labeling

As a musician, a performer/composer who comes from a classical violinist background who is also composing, I face this almost everyday: labeling and categorizing of my identity as a musician.

I am not frustrated, but rather puzzled.  People have the need to put you into a "line" or a "box" where it can be "shopped" in stores.  A few weeks ago I posted about "Head Space" saying that I have known performer/composers who stopped performing other people's music.  I was thinking in particular about one person whom I looked to as kind of a model, although he isn't a violinist.   Yesterday I was told that this person HAD to stop performing other people's music in the 70s and 80s, since that was the only way to be taken seriously as a composer!!!!  WHAT. THE....

I am not sure if this is entirely true, but 3 decades later, if I am puzzled being asked, "So, you are a performer.  AND a composer, right?"  as if that is something extra-terrestrial (never mind Vivaldi, Corelli, Paganini and the gang) I am just wondering, WHEN in the world, this "categorizing" has become a norm, and being both performer and composer in classical music world has become a novelty; just in the 1900s?

If I were in charge of conservatory education, I think I would like to see that all performers are REQUIRED to compose and improvise, both.  You learn so much about performance by understanding composition, or the process of composition.   I am not saying that all performers need to be Ligeti or Boulez :)  But wouldn't it be so much more fun to liberate ourselves creatively?   On the other hand, "all composers must interpret and improvise" might not work, but still they are, as I hope, required to play at least one instrument.  I do think though, if a composer could be an instrumental performer at the level who can give a public performance, that might actually help their compositions.

Would it be possible to have a structure where performance and composition world can have more fluid relationship?