I made most of my own clothes starting when I was about 8 -- I did it because it was cheaper to buy fabric and thread. I had 3 or 4 patterns that I modified to make everything I needed. I did a 5/8" seam, but now I see that many folks use 1/2" seam. For knits using a serger I believe I have heard you can do 3/8". I was told when I started quilting that the reason we use a 1/4" seam is that the quilt top is secured with stitching so there is not enough stress on seams to cause them to ravel. I was also told that when you tie a quilt you should allow a 1/2" seam allowance so the seams don't come apart with a lot of wear (I am repairing an tied baby quilt now that raveled pretty bad).