> [...] it helps me understand how this person's previous employer valued them.
Some people's skills/value increase at a rate greater than most employers are willing to match in compensation. These fast learners are the exact people you want to hire, aren't they? Yet the metric of previous salary is pushing you in the opposite direction, toward undervaluing them. Why even check the number if it gives you the wrong signal? Some other employer may not bother to ask, form a more accurate judgment of the person's value, and snatch them up at a rate you were unwilling to offer.
Some people's skills/value increase at a rate greater than most employers are willing to match in compensation. These fast learners are the exact people you want to hire, aren't they? Yet the metric of previous salary is pushing you in the opposite direction, toward undervaluing them. Why even check the number if it gives you the wrong signal? Some other employer may not bother to ask, form a more accurate judgment of the person's value, and snatch them up at a rate you were unwilling to offer.