Who says companies want the "highest quality candidates?" Some companies would prefer desperate, obedient employees who have no other options and will jump through any hoops they're told to jump through.

Many companies exist in a state of this reality. Very few people at these companies genuinely want it. There are some companies that are clearly and intentionally designed to want this, but they're very rare (oftentimes in consulting, oftentimes companies which prey on visa programs or undocumented immigrants. oh, and amazon).

The goal of recruiting at most companies is to get the best candidate for the role at the best price within the time it is feasible to recruit for.

Also, most of us are about average.