Preamps. Do we really need them?

I've been shopping for a new preamp lately, reading the forums, etc. If I have only one source, a DAC into which all my digital components feed into, do I really need a preamp and not just a volume control. After all, that's all I really need from a preamp. I've heard about passive rigs that just control volume, or attenuate it. I understand that you lose some volume if, the source's output isn't enough to drive the amp staight. I'm willing to make that sacrifice.