Customizable Table Columns

It's not that it's too complex to program.

It's too complex for the user. If someone opens the preferences and it presents them with a giant string of gibberish, Cog becomes more difficult to use. A drag and drop approach may work, but would be too complex to program (Or, at least I wouldn't be doing it).

In the end it would just be a seldom used feature that just adds lot of unnecessary complexity.

ground for doing it - there's many people switching from pc to mac (me is one of them) and they will (or already do) lack usual look of playlists, as under window$ almost all players have this
you even can make non-customizable with built-in template "Artist - Title" and this will make things easier

PS. ten years habit is a hard thing to overcome

What does this allow you to do that you can't currently do in Cog? I don't think I understand, either.