Laziness -- brute force (exhaustive combination) is perhaps easiest to code (although first fit decreasing is pretty easy)

Impatience -- exhaustive combination dies a horrible flaming death somewhere in the high teens, unless your computer is a lot faster than mine. First Fit Decreasing needs a sort, but that isn't a big deal until you get into too many DVDs to want to hand process.

Hubris -- exhaustive combination will achieve the optimal result, but first fit decreasing will come within 11% of it. What price glory?