If we want them here on their merits, why do we care if they’re “married” or planning to be “married” to one of our citizens?
What is this “merits” nonsense you keep talking about? We don't let people immigrate based on their merits. There is no “merit visa.” Our immigration laws are a confusing mess and there are exception to exceptions, but for the most part you cannot come to the U.S. as an immigrant unless you have close family here. You might be able to come as a tourist or a student, but not as an immigrant. Employment based visas, like the H-1B visa, are nonimmigrant visas. If you just want immigrate to the United States and you have no family here, odds are you will not ever get a visa, no matter how awesome a person you might be or how meritorious your life has been.
Let me give you a specific example. I spoke with a young man the other day who recently come back from a tour of duty Iraq. While he was there he met a Filipino lady working there in some sort of contract job in support of the war effort. I don't remember what her job was exactly, but it was something fancy. She has several advanced degrees and speaks several languages fluently. She's a really bright lady. Anyway, those two want to get married and he is in the process of doing a K-1 fiance visa to get her over here. Now, if that K-1 visa was not available, she'd never be able to come. She has no family here. Filipinos aren't even eligible to participate in the visa lottery program where they have a tiny chance of getting a visa without family in this country. Even if she had a citizen brother or sister in the U.S. who could sponsor her, she'd be looking at something like 20 years or more before she could come over. The only way she's going to be able to come over is with that K-1 fiance visa. She could be Mother Theresa but she's still never coming over just on her merits.
Do you see what I'm saying here? There is no “merit visa.” Most people in the world could never get an immigrant visa allowing them to move to the U.S. There is a very limited visa lottery program where a few visas are given out every year to “promote diversity,” but only a tiny few visas are awarded relative to the number of people who put their names in the hat, and several countries are excluded from the program because more than 50,000 immigrants have come in from those countries within the five years preceding the drawing. So Mexicans, Canadians, Chinese, Indians, Filipinos, people from the U.K. and several other countries like that from which we get a lot of immigrants will never be eligible to participate in the visa lottery program. The only way these people are going to get in is through family based immigrant petitions or by coming over here on a work visa like an H-1B and shooting for legal permanent resident status, converting from nonimmigrant to immigrant status, after being here for several years. No one just gets to move here on their merits because they are good people. It just doesn't work that way.