It's not that the Koreans are the only one's doing this. It's that they were the first to hit by this very new interpretation of the law. Now that this interpretation is public i don't think anyone's going to the US for conferences/trade shows/general business trips for a few years.
This new extremely strict interpretation means that the only safe way to travel to the USA for work is on a h1-b or similar heavyweight working visas.
This is fine if you wish to interpret it this strictly. There are of course consequences and as noted by many many non-US people above the ESTA business visa waiver is near worthless under such strict interpretation. Which means no more short term trips to the US office nor conferences or trade shows. The lack of something lighter weight than a full working visa for these sorts of things means the USA is closed for business.
What is “these sorts of things” to you? To me building factories and installing equipment on the factory floor is a different class of work that is generally prohibited under the lighter options like ESTA or a B1 visa. Here is what B1 allows as an example:
Consulting with business associates
Traveling for a scientific, educational, professional or business convention, or a conference on specific dates
Settling an estate
Negotiating a contract
Participating in short-term training
Transiting through the United States: certain persons may transit the United States with a B-1 visa
Deadheading: certain air crewmen may enter the United States as deadhead crew with a B-1 visa
I think many non-US residents observing this would be on the side of not trusting ice and are now less willing to travel to the USA for a work trip on a visa waiver.
It is claimed that their work has exceeded the limits of B1.