I am mixed , sometimes I design my own .. sometimes I buy a pattern. I have been known to buy patterns for some very easy quilts , for a couple of reasons.. 1. Sometimes I do not want to think I just want to cut and sew. #2. I often do not trust my math, and end up buying more fabric than is needed... at the price of fabric ... its easier and often cheaper to buy the pattern with the fabric requirements, than over buying!
Do what makes you happy and gives you the results you want.