Bias binding is necessary if you ever want to make a quilt with a scalloped edge, and it is a bit laborious to cut, vs the usual straight grain cuts. I have made one doll-size scalloped edge quilt ever, and used a fabric that occurred elsewhere in the quilt, so probably wouldn't have bought ready made binding even for that, but it's kind of nice to know it's out there if I ever get lazy or rushed. One thing someone pointed out about bias binding is that it wears better than straight grain. If there's a thread that runs along the edge of your quilt it's more likely to make a long tear if it breaks whereas a bias results in a crisscross pattern of threads all along the edge, and if one thread breaks it only goes a few inches.