Your salary negotiation point speaks more to a call for open salary data, which many people have been arguing for.
You're missing a lot with your second point though. If a company has excellent salary data and can put in you a band, then it also means that you have better grounds to argue for raises when you gain experience, or argue if you are underpaid, or even find jobs at companies who intentionally pay a higher percentile to market as a way to attract better talent.
In contrast, if we all operate 100% blind with no data, as many here seem to want, it would lead to all sorts of unfair wage situations with people doing equivalent jobs earning vastly different amounts. This sort of environment is biased towards more aggressive people who have strong social skills when it comes to negotiation. In fact, you see exactly this when companies choose not to buy data like this to set their bands.