[te_chris]

Partly yes, but also because of the data requirements of the format (CD). Bit depth is important too because it defines the number of locus points available to you when measuring a wave, so the more bit depth you get the closer the digital representation of the wave becomes to the original analogue source.

This is a point that often gets lost in these discussions: the whole point of digital audio is mean't to be a more efficient capturing and distribution of analogue source, as such the more information you can capture about each instance in time the closer your digital reproduction can get to the original analogue wave.