If I just use a DAC, do I need a Pre-amp?

I recently asked a Facebook group this same question.  I should have asked audio forum folks first.  Sorry if there is overlap.

If I only use DACs for my amp, why do I need a Pre-amp?
I have the opportunity to get a nice Fisher 400CX-2...but why?

I have volume control on my Fiio M15, and volume via my player for my Chord Qutest.  How will a pre-amp make things better.