I've sometimes bought pieces that caught my eye but I wasn't totally in love with. After awhile as I started to buy fabrics that I was totally in love with I weeded thru those other pieces.
Some I held onto after looking them over again to use for pieced backings. Others in the pile I now use to make practice blocks or practice various pattern shapes, then I still have scraps for all the other ideas floating in my head for my "one-of-these-days" list of projects.
So it all never really goes to waste in the end.