I started out with the attitude, everything cut good, sewed good, creates square blocks. And all was good. It also, helps to have the same amount of seams in each block.
And then, I made some half square triangles. OMG! I had to square those little guys up. They slid, stretched, ran and more. (Wish I had known about the starch it stiff method. Haven't tried it but will soon.) That experience with the HSTs has made me into a person who makes sure everything is square every step of the way. Each part must fit as perfectly as possible, otherwise, some ripply, wiggly, cupping blocks occur. I overcut and stitch scant 1/4" seams and still have to square up.
Some don't square anything and still make beautiful quilts. It all comes down to what works for you.