Disparate Impact is one of the most illiberal policies in America. Companies need to be so careful that their results can't be construed as discriminatory that they need to go out of their way to make their hiring practices discriminatory. You could have a totally blind hiring process (remove names from resumes, modulate voices in phone interviews, never get any indication of race/sex/age of applicant) and still be liable for a lawsuit if you don't hit the arbitrary "80% rule" benchmark.

The Disparate Treatment and Disparate Impact doctrines are diametrically opposed, yet both can lead to lawsuits. When a company gets big enough, it's going to start running into discrimination lawsuits no matter what they do. There are things they can do to offset the damages (diversity training, diversity department, certain types of donations), but the end result can still be settlements in the tens of millions of dollars.