What's the problem with background screening companies?

I dealt with a couple of them, and they were dangerously unprofessional.

One was emailing Word documents asking to fill in personal information while the footer of the same email was urging recipients to never share personal information by email.

Another one was asking US-specific questions while I was in Europe.

Their IT is abysmal and their English is barely understandable.

But they endure and manage to sell their services for dozens of years.

A collateral question is, why businesses do these background checks to start with?