Pac-Man, I don’t agree that there’s “nothing wrong” with frum couples not applying for a marriage license (even if it’s not illegal), which is why I wrote that there “may not be” any problem with that. But I am glad you agree that even couples who are not legally married are required to report all household income.
However (and this question is for GAW or anyone else familiar with the practice of not obtaining marriage licenses for monogamous marriages), if the family reports all household income as they are legally required to do, how does not getting a marriage license entitle them to greater government benefits?