As far as the Nigerian pig fucker, having worked with a few of them, lord knows he'll fuck anything with pulse that's remotely thinner than she is. He'll never leave her as they are very family centric, but it is obvious he'll fuck anything that moves.  That's exactly it.  Just because he'll marry you doesn't mean he has any intentions to be faithful.    That might be the secret to "why do pigfuckers marry pigs?"  I didn't think of it before, but you're onto something.