I buy charm packs because they are good fillers when you just need a small piece (less than 5"), the jelly rolls are also great when making quilts that are meant to be (ab)used, such as a baby quilt. I used to buy fabrics by the yard, then realized that when I want to make another project none of the leftovers are the right colors that I need, so now I just buy fat quarters or linear quarters. Besides when you buy the pre-cuts, the patterns and colorways are already coordinated so there's hardly any need to go through the fabric bolts trying to match colors.