Many people seem to think that test charts are being used as a substitute for real life use and get all bent out of shape about it.
A test chart is to evaluate what a lens/camera is capable of under ideal, controlled conditions that can be replicated by other users. It can show real issues which are nearly impossible to quantify when shooting birds, landscapes or sports. Does a great lens chart photo mean it's a great lens? No. It means that we have some idea of how sharp and repeatable the lens is under ideal conditions. If it fails the chart test (won't focus, decentered, poor resolution) then you may have issues with the lens in real life. Better to know that before you shoot that once-in-a-lifetime event.
I always test my new lenses before shooting a critical event for the first time because that way I know there are no mechanical/optical defects which will surprise me later. If you want to slap that lens on your camera, don't check MFA or focus, and shoot away, fine. I salute your trust in the equipment. I like to run a test where if there's a problem, I can attempt to isolate it rather than being puzzled about why half of my photos are out of focus. Did that blade of grass confuse the AF? Was I holding the camera perfectly steady? Or is the lens a piece of junk?