And if I fully understood all the complexities of something before beginning, I'd be too intimidated to begin anything.
From my own life experience I think it is better to understand the complexities of a topic (be it in politics, economy, religion, human interaction, software design) beforehand. Once you know the complexities, it is much simpler to find solutions.
I believed for too many years in simplicity. The problem with simplicity is that it produces too many exceptions and trying to get hold of all arising exceptions is quite time consuming and costly.
Life (and programming) is simply not good or bad, black or white etc.
Just one example from my own experience: Deploying 12'000 pc's with 3000 applications in 25 different countries is simply a very complex undertaking. Trying to simplify too much, means running into plenty of difficulties...
And of course it is very important to know the difference, when things are simple or complex
In the case of cover art storing I agree with Matt that storing inside the file is much simpler than outside ( I have all my cover art that way). But then it would make all those users unhappy that want to store more than one file per track!