I have read it. I don’t think you get my point. I said ‘access to’. If you think about it, there is plenty of data freely available about the company in most job applications (often including actual salaries they pay their staff - literally the most pertinent data). Yes, employers will use whatever tools they can to guess at what you might accept. It’s a negotiation.
It is perfectly possible for both sides to approach a salary conversation as the negotiation that it clearly is. In reality, many job candidates barely think about negotiating the salary, but I doubt that’s due to not having enough data points. I think it’s probably more to do with not wanting to be perceived as ‘greedy’ or some other moral badness, and finding it more comfortable to let the recruiter/employer play them like a fiddle. Moral pride to spite their face. Sure, we can feel good in the moment by angrily pointing out that companies take various measures to maximise income and minimise expenditure, as if it’s surprising or ‘wrong’. But it might also be helpful to remember that we are in exactly the same situation. Then perhaps we can start negotiating better deals for ourselves, thus improving life for ourselves and our dependents.