For instance, whereas before when salaries weren't explicit, a weaker candidate with some good qualities who was on the bubble for consideration might be able to get a job if the salary was more favorable than the company was initially planning. With explicit salary ranges, if the candidate isn't deemed good enough to warrant hitting that predefined range, they might be unemployable in that field and not gain the experience needed to progress. In the past, a weaker candidate might have been able to go for a lesser salary range, get the job and gain more experience, and maybe make it up down the line. Maybe that's no longer a path forward for a lot of people on the bubble.
And stronger candidates who are perfect fits and world-class performers might be lost for a lot of companies because the company has the excuse of a pre-defined salary range. So maybe firms miss out on some genius, perfect fits, because the bean counters can't be bothered to assess everybody's merits individually.