Is my boss trying to hold me back?

Hello all, can anyone help me understand my bosses motivations with me. I am qualified in a subject area but my boss always puts me in another subject area instead of allowing me to shine further in my subject area of specialism. Any ideas as to why more than this?

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+1 y
My thinking is that because allowing to further develop in my specialism may lead to me leaving the team and him effectively losing his assistant.
Is my boss trying to hold me back?
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