When I've applied for jobs and done salary negotiations, I try pretty hard to find out the max I can get using as many variables that I think are relevant (e.g. years of experience, previous companies I've worked for, projects I've contributed to, etc). No one is writing an article trying to expose me for this.

I think the concern is how invasive they can be when doing this. It's one thing to quickly search your name on Google or something, but they can do creepier stuff. They can look at many, many more variables that I can, and it's a little creepy. It seems a little wrong to use peoples' credit scores in order to squeeze down a lower salary. I don't think there's anything even remotely comparable that a prospective employee can do.

You have less data than the company

The internet has information on what salaries a company pays. One would be foolish to not look it up before negotiating compensation.