It's not the most likely they are doing it for. There are a lot of Americans that get married in the Philippines. If you pulled a CENOMAR on me you would get a CEMAR saying that I am married. Unless I get divorced or annulled and have it legally recognized in the Philippines (very long and expensive process), or am widowed, I cannot get a visa for another Filipina. Believe me there are people that try and that is the reason for the requirement.