I don't often buy precuts, but I fully understand why people like to buy layer cakes, jelly rolls, etc. You get an assortment of all the fabrics in the line! I have wound up with a few, and I use them, often fussing (cussing?) because of the pinked edges or the inability to prewash, but I've never been unable to make the pattern work with the precuts, and I'm happy that I had the variety of fabrics to work with.
I'm wondering - when people say they "make their own" layer cakes, do they really mean that? Do they actually cut 10" squares out of 20 or so fabrics?