My thoughts on sham marriages first of all is that since they are illegal I really do not understand why a person would allow such a skeleton in their closet. I do not do illegal things. Someone may think they can get away with it, and many will get away with it. But what about the sleepless nights of guilt that will come one day when they realize this could prevent them from pursuing some career path or other opportunity? A fraud on your record can have serious consequences in your future. It may lie quietly for years, and is always at risk of being unearthed. That's just the practical consequences.
And then there's cynicism about marriage and relationships, another thing I want no part of. I'm not a romantic, because romanticism is too shallow. I'm a practical realist, and I respect marriage as a working and integral part of my life and identity. But for other people it's just another superficial form with little meaning, apparently. Pity. I don't even like people, honestly, because most allow themselves to be low, untrustworthy trash. But if you do value the best that humans can be, a marriage with or without children is one the prime places people have an opportunity to rise to the heights of human capacity, much in contrast to users who use people and such structures to perpetrate a fraud.
It seems for some people this kind of fraud becomes okay because they have seen someone else do it. That old peer pressure thing where because someone else did something idiotic, it might seem to be normal or even cool. "Don't judge me" someone said in a post where they sought help in managing their sham marriage, and posted openly about it. (Not with a real name though. Too bad.) Yes, I judge, because it is a legal fraud and it is wrong in so many ways.
... but people that are fraudulent know they are and these kind of people don't have a conscience that keeps them up at night. They think about themselves and what they will get from it 'short term'.