This is so irresponsible of you to just assert without evidence, and is so out of context to portray VW as the good guys here. They did not break the rules and flaunt regulations to make their system more efficient. They did so to cover up their failure to deliver on a new generation of "clean diesel" tech. VW thought they could do it, they invested billions in it, and they couldn't figure out how to do it without emitting way too many other pollutants. So they built their cars to lie to regulators.
The tests cover an extensive range of use cases, mostly warm running. There were two modes, one that was more fuel efficient but emitted NOx above regulations, and one that was less fuel efficient but was within NOx regulations. They detected when the tires were on suspension that simulates real-world driving for testing. They got caught by academics who wanted to test real-world vs simulated suspension.
Here is actual source, Bloomberg, which isn't some kind of environmentalist or anti-business publication: (https://web.archive.org/web/20160312181801/https://www.bloom...):
"The road tests captured a variety of conditions: high elevations up Mt. Baldy; stop-and-go urban errand-running in San Diego; freeway driving around Los Angeles. The two Volkswagens’ emissions exceeded standards by 5 to 35 times. The BMW’s didn’t. [...] The Lean NOx Trap is a system of concessions. To get cleaner exhaust, you’d need to use a squirt of fuel every few seconds to burn up nitrogen oxide. Or, in the other direction, to get better fuel efficiency, you’d need to spew out dirtier exhaust. Managing this trade-off requires a complex calibration of the onboard computer, the engine control unit, so it can adjust constantly to variables like temperature and speed and optimize both emissions and fuel usage. The trouble was, Volkswagen hadn’t been able to get its new engines to comply with the stringent U.S. standards."
The reason is they had invested in a "clean diesel" engine tech that was supposed to be their market differentiator. VW invested billions into it. Yes, it was more fuel efficient, but it was supposed to also stay within existing pollution emissions regulations. Nobody else made such big investments in clean diesel because they couldn't figure out how to make it more efficient without also emitting pollutants at much higher levels. But everybody was so bought into it that they felt they had to cover it up.