Why does the U.S. immigration system care whether a marriage is a “sincere” or “real” relationship?
As an immigrant myself, who came to this country through family ties (not marriage), me answering this question might sound self-serving. The fact that I had to mention "not through marriage" shows my own insecurity facing possible scrutiny or people dismissing my answer. But I feel that (as I usually do when I came to questions like this) I'm obligated to say something. So here it is, take it as whatever you want. Being a first generation immigrant who just so happen also knows a lot of other first generation immigrants, I heard a lot of horror stories about marriage green card from both sides. There're people who genuinely in love, but scrutinized by the immigration. I heard a girl's heart breaking tale of her boyfriend of 4 years refuse to marry her until she get green card through her work, because "I don't want marry you so you can get a visa, I want our marriage to be pure". I also heard horror tales of people get cheated by their husbands and wives who requested a divorce right after the 3 year conditional green card period has been met. And I heard horror tales of women being controlled, abused by their citizen husband using deportation as a threat to keep them in loveless and abusive relationships. There're no ends to these stories, just like usual relationships. You rare heard good ones, it's the bad ones that made into the after dinner gossip. And I often wonder, is these process really work? Does it really filter out the "fake" marriage? Or it simply creating unnecessary pressure for people who are already struggle with their lives. I often wondered, why immigration marriages are held to a higher standard than regular marriages. Just like why adoption parents are heavily scrutinized while irresponsible people are free (or even encouraged) to have children. It seems unfair. And then I realized, in both situation, the end result (citizenship through marriage or child adoption) is considered a reward, to which people must strive to achieve. For families cannot have children of their own, having children are a privilege granted to them, and they need to prove themselves to be worthy of such award. And the same thing goes to a foreigner who wants to get into the US. The citizenship of United States of America is an award, a privilege, a prize, to which a foreigner must prove him/herself to be worthy to get that award. In case of special achievement (which how my family got into US) my dad had to prove his ability can contribute to US society in such a way that no one else can. And in the case of citizenship through marriage, you need to prove your love towards the citizen is real and sincere. It's not the marriage that's under gone scrutiny, it is the foreigner who wants to get citizenship through marriage. After all, citizenship is something only the natural born Americans deserve to have, everyone else who wants to get into this great nation needs to go through loops and hoops. This isn't unique of US, of course. Almost ALL countries in the world considered their citizenship as a privilege to other people, and foreigners need to meet extra conditions to be "deserving" of such privilege. There's nothing wrong about it, really. A country when absorbing people from other places naturally only want to best and/or people of special skills that could benefit the country. And we also need to realize all immigration law's primary goal is to protect its own citizen. This protection can be heavy scrutiny of foreigners entering the country for long term stay or visit, just to make sure they presents no security risk towards citizens. Naturally the government would ask if the visitor or immigrate has criminal history or terrorist ties. This protection can be rules set up for companies that only allow them to hire immigrants when they can't find citizens to fill the position. This protection can be scrutinize their marriage to make sure their own citizen don't get cheated on. And that's why the immigration officer act as if all people married into US are scheming gold diggers. The purpose of marriage immigration law is very different from the purpose of civil marriage law. A civil marriage law protects both parties, while the immigration law protects its citizens but not their soon-to-be (or already are) significant others, who are not a citizen yet. Even after the immigrant gets into the country through marriage, until he/she became a full citizen, the law still protects the citizen not the immigrants. After all, if the citizen want a divorce, it's the immigrant will get deported back to whatever hellhole her dear white husband drag her sorry ass out of. (I used this language and gender pronouns on purpose*). So the original idea of allowing marriage immigration is so that if a citizen met someone outside their country and started a relationship, he/she has the power to continue this relationship after he/she decided to return to his/her home country. Sure, a civil marriage is a basic human rights for citizen. Regardless of what reason, two people can get married (with a few exceptions). However, while the marriage involving a foreigner is a right for the citizen, the said foreigner getting citizenship or green card through this marriage is NOT a human right. like I said at the beginning of this answer, it is a privilege. In case a citizen marrying a foreigner and the foreigner end up maintaining his/her original citizenship, and probably only visit his/her significant other, the couple won't have any problems, there's no forms to fill out, no conditional green card to maintain. It's ONLY when the foreigner want immigrate and get the privilege of becoming a citizen through marriage, the said marriage would go through scrutiny. Now imagine American government is like an overbearing overprotective mother, while her precious son can marry any girls from her own community, if he brought back some weird girl from a faraway land with unknown intention, surely she'd have her son's interests in mind and check out the girl thoroughly. US immigration is that overbearing and overprotective mother who set up ridiculous, old fashioned and often useless rules to measure the unknown son/daughter-in-law who would enter her home, become part of her family, while totally OK with cousin Jack marry cousin Joan after both of them got drunk in Vegas. After all, cousin Jack and Joan might not be the smartest tool in the shed, they're family.And that's why US immigration system care about whether a marriage is sincere or not.*The reason I got heavy handed with language because it is what I heard the most when it comes to marriage involving immigrants, especially marriage that brought an immigrant into the country. As an Asian women, I had too many horror tales of mail order wives or international dating sites where a woman was brought over and be mistreated, while got no sympathy from anyone. People believe since she came over under false pretenses, she deserve to be abused. While many American marriages are formed under false pretenses, carelessness and stupidity, people seem more sympathetic if there's domestic abuse. It really is very sad.