Earlier quoted context omitted.
Because the sooner you get to the top of your budgeted salary the more years you spend collecting it. Collecting a higher salary for longer makes you more money.
Ah I see! The assumption is that the candidate is already worth the top of the pay range for the position. In that case, should they be aiming for a higher position? Should there be room to grow in the position?
I'm not sure where "The assumption is that the candidate is already worth the top of the pay range for the position" comes into this. As a potential employee, i want to maximize my $$$. How much the employer thinks i'm worth is the employer's problem not mine. If the employer gives me a choice that i can either (a) make more money or (b) make less money, i am going to choose (a), and i don't know why anyone would chose (b), all other things being equal.