A handful of point releases ago, Apple added the ability for iTunes to retrieve your album artwork from their servers if it wasn't already embedded in your MP3 (which, chances were, it wasn't). It would seem the point of this is to make a feature like Cover Flow, which is how you actually look for CDs in real life, much more valuable:
For these screen shots, I used my purchased music because most of the music I ripped from my own CDs look like this in Cover Flow:
Cool new feature? Yes.
Life altering experience? Not so much.
I suspect the next generation of iPods will probably have a Cover Flow interface though.