Why don’t we see grades of Brisket lower than Select? Couldn’t a USDA Commercial brisket be just as good as Prime or Choice?

Based off this grading scale, wouldn’t USDA Commercial have potential marbling equal to USDA Prime or Choice but just an older cow? And wouldn’t USDA Standard beef potentially be be equal to Choice or Select? I know that cows need to be a certain age to qualify for Prime, Choice, and Select. But theoretically wouldn’t a cow that would’ve have been Prime but older than 18 months still be good eating?

I’ve eaten ungraded Ribeyes and NY Strips and have gotten some pretty marbled cuts and some pretty poor cuts. I imagine the same would happen for Briskets?

Based off this grading scale, wouldn’t USDA Commercial have potential marbling equal to USDA Prime or Choice but just an older cow? And wouldn’t USDA Standard beef potentially be be equal to Choice or Select? I know that cows need to be a certain age to qualify for Prime, Choice, and Select. But theoretically wouldn’t a cow that would’ve have been Prime but older than 18 months still be good eating?

I’ve eaten ungraded Ribeyes and NY Strips and have gotten some pretty marbled cuts and some pretty poor cuts. I imagine the same would happen for Briskets?