There is always the accountants.
I used to pick up brand new S76As from the Ro-Ro and after they had been fitted to NS standard air test them and take them up to Aberdeen. We had a contract on Rhode Island which terminated and the S61 and 76 involved came to the UK.
The 76 was fitted with Loran instead of Decca so the Decca was installed---------- and the DME was removed? Why? There is no requirement for DME, ranges can be given by Decca and if the DME went wrong it would cost money to fix it.
About a month later the Norwegian CAA mandated DME as the range indicator so all the aircraft had to be fitted with DME including this 76 but a different instrument because they had flogged the old one.
And so it will be with NVGs.
They will have to be certified. It is for Public Transport use and the rules are different from SAR, police and medical services. It is the same with winching. There are a different set of rules regarding that after an S61 arrived on the back of a supply boat that it was winching off so now one has to have the capability to complete the immediate winching operation and fly away despite an engine failure.
This will cost money, lots of it. EASA or the CAA will want to fly and see it in operation in various levels of darkness before they will issue a clearance and somebody will have to pay. The helicopter companies wont so it will be up to the customer to assess whether it would be worth the expense.
Enter the accountants.
They will run a cost evaluation comparing money forked out and money saved and the result, because there are so few occurrences where NVGs would have helped, would mean that it would be rejected unless you can prove that people are going to die without it.
It follows that nobody is going to pay for the Certification so for Public Transport, North Sea, it just wont come.