It would be a shame if the US regulations did prohibit use if IMC.
I agree with Crabs statement about using the goggles while IMC but flirting with VMC especially if it is desired to transition to VMC. They make this safer although you have to be very aware of the limitations such as thinking you are VMC when you are not. Even if IMC but able to see, while not using the goggles as prime reference, you are much better prepared for a serious emergency requiring immediate descent or landing.
If I’m in deep cloud enroute IMC I do not have the goggles down but they are on my head ready to go. I’d rather not have them on for comfort….