Mathematica doesn't simplify even providing the assumption

Question

I wrote the following:
$Assumptions = {nAvg >= 0};
Simplify[Im[1/(8 nAvg)]]

And Mathematica returns me: 1/8 Im[1/nAvg]
Why doesn't it simply returns me $0$ ?

cvgmt · Answer

$Assumptions = {nAvg > 0};
Simplify[Im[1/(8 nAvg)]]

$Assumptions = nAvg ∈ PositiveReals;
Simplify[Im[1/(8 nAvg)]]

Maybe when nAvg==0,1/(8 nAvg) will return Complex Infinity.
Other way such as
ComplexExpand[Im[1/(8 nAvg)]]
ComplexExpand[Re[1/(8 nAvg)]]
ComplexExpand[ReIm[1/(8 nAvg)]]

work since ComplexExpand assume all the variables is in Reals.

Mathematica doesn't simplify even providing the assumption

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