I have to admit I don't understand why companies are so opposed to this. Companies I've worked at have ranges of salary internally, which presumably they could share. The ranges are large enough that I think employees would struggle to use them to negotiate very well. And employees talk salary to each other and have other ways of getting that info anyway.

Edit: someone else pointed out that Accenture does this in one of their listings:

"For the state of Colorado only, the range of starting pay for this role is $58,700 - $94,1999" https://www.accenture.com/us-en/careers/jobdetails?id=964186...

Here we see there's even a benefit: Accenture will save time interviewing people who don't want to work for these horrible low wages.