I buy fabric because I like it, and have built a nice stash over the years. Very handy now that fabric prices have shot up so high. I shop from my stash first, then fill in if I need to.
I like to design my quilt first, then go to my stash to see what fits. Since I make a lot of scrappy quilts, value and color are more important than yardage. The only time I worry about yardage is when doing borders.
Sometimes when I see that I have 3+ yards of fabrics that go together, them I may plan a quilt around those fabrics.
So to answer your question, I would have to say, "It depends,"