If predictive power doesn't matter why do we need any of these systems at all? We could just randomly assign people with numbers from 1-10 and be done with it.

If predictive power doesn't matter why do we need any of these systems at all? We could just randomly assign people with numbers from 1-10 and be done with it. You are type 7. I am type 3. Now you can go ahead and assign whatever properties you like to these types and be happy.