Ranges are still somewhat useful. If they low-ball the upper bound, anyone expecting close or above the upper bound is unlikely to apply. So there is incentive to be honest about that end at least. But as an applicant (or current employee), knowing the upper bound the company is willing to pay for this position is useful information for salary negotiations (and to enable you to spend your limited time and resources in applying to well-paid jobs)

Obviously it's not perfect. But as you say, it's a difficult problem. And salary ranges are at least something