Maximizing profit.

It's a large chunk of logistics. When EDL (electronic data logging) became mandatory a crapton of drivers left the industry because they could no longer fudge records.

The labor churn is an unintended, and ignored side effect.

I think they're definitely trying to maximize _cause_ for firings, such that if and when they do firings, they can't (as easily) be accused of firing for wrongful cause.