[Flac] Why is flac playback more quiet than .wav?

[Bob]

If I rip a cd and encode to flac why does it sound quiet (25-30% less
volume) compared to de-encoding the flac file back to wav and playing
wav directly with winamp.  All volume slider settings stay the same. 
The soundstage sounds flat as well as if there no juice behind it,
even when the volume it turned up to compensate.  What's the
difference and why should playback of flacs be treated any different
than wav?  There's nothing wrong with the file if it can be converted
back to wav with what sounds like better playback results,  Is there
some setting that need to be adjusted in the codec to compensate?

Flac v1.1.1