I look at it as the fisherman. You prepare your material to build your boat. You use the best for your boat. The cut offs that weren't good enough for the boat you use for stools and stuff, it's already prepared after all. We do the same with shop fixtures, some of us anyway. A knot in your boat may be a problem, not so much in a stool seat. Why spend a lot of time on something that may not last just throw a few legs in it and go. That doesn't mean that we can't refine something simple and make it beautiful.
Jim