thisislife2Employers use your personal data to figure out the lowest salary you'll accept
I'm not seeing how this matters, they were already doing that - the market is a big auction to work out the overlap between lowest salary employees will work for and the highest salary employers will offer. In that process employees also use data to figure out the highest salary that will be offered. The thing forcing employers to pay the salary they do is that if they offer less someone else will gazump them for the employee's time. It has nothing to do with the circumstances of the employees lifestyle. The lifestyle adjusts to the salary.
If that’s true and this has a null effect, why would a business pay for it? There must be some utility for them. Like others already pointed out: information asymmetry undermines worker’s ability to negotiate, resulting in lower wages for everyone.