When I was riding motorcycles in the foothills of the Sierras, there was a couple I used to ride with. Sometimes the husband would not go with us and my wife did not think it was appropriate for me to be out riding with her alone. She was/is a competent rider and we both enjoyed the same kind of roads and rode many times together.

I don't think my wife thought we were fooling around or anything. More like she was jealous that I had a passion for something that I shared with another woman. She never got used to it but I think she also realized that we are not going to enjoy everything that the other does and it's ok to have some interests/activities that you're spouse has no interest in. As long as it doesn't start to take you away from your spouse for too much time, I don't see why they shouldn't get over it.