Think of it this way;
In real life, there is not a player with a 19 DUR hanging above his head telling a GM or manager that if you play this guy 500AB, he's going to get destroyed. Instead, they're going to try to play him 500AB, he'll get destroyed, and the public laments what could have been if he hadn't been so fragile.
Instead, you have that number hanging above his head so you know that you can only play him 150AB, and maybe get him to do that for 15 seasons.
Really, it's a damn shame that Fidrych didn't have a 9 above his head, or he'd still be throwing 45 innings a year.