Preamps - Active, passive...???

I have seen a number of comments in magazines as well as on-line about preamps as an "unnecessary evil", (my words).

There are products such as Volume Controls and Passive Preamps that are supposedly designed to be as simple as possible; thereby changes to the signal are to be minimal. My question is, "Why then would you buy an active preamp, IF these "simplistic" devices are "better""?

Let me state that I am not ridiculing anyone for there purchases. I am in a state a flux in my stereo and the preamp department leaves me scratching my head. Such as, is something simple, such as a Plactte passive the way to go or a highly rated active preamp.

Thanks in advance for your comments.