Well, they have been cheating for so long in places like NY, Detroit, Philly, Chicago, that they just get lazy about it. Why bother covering your tracks when you know that nobody cares enough to even try to catch you?
^^THIS^^
Also, anything that works and is easy will be scaled up.
As soon as they try to scale it up, they run into the problem of hiring quality people, just like any organization.
The imperative of the mission (cheating) takes precedence over anything else though, so inevitably some of the new, low-quality hires will screw up.