I should also say they are both in very high paying jobs and not at all in need of stuff I don't think. We are also quite financially secure to tho so it isn't about not affording something at all either. They also have chosen to marry a long way from home so maybe they don't want to lug it all back???
You could donate to charity in their name for a cause you know they both believe in?
My sis and BIL are both pilots on good incomes and donated to royal flying doctor service for example