As strange as this question may sound, we are in fact asked this on a fairly regular basis. One’s first reaction upon hearing this question normally falls into the category of amusing things like this person must not like their spouse, or this person must be having marital problems, or this person must be up to some devious kind of activity.
While all of these are possibly true and in fact we have seen situations in which they were exactly the reason for the question, there are also a number of reasons why an individual might not want their spouse to become a permanent resident. They relate to things such as their may be tax reasons why that individuals spouse does not want to become a permanent resident, or there may be issues where that spouse is not able to come to the US at the present time due to family obligations overseas, or in some situations the spouse simply does not want to.
One of the requirement of becoming a permanent resident is that the applicant must have the intent to remain permanently in the United States. Any significant time spent outside the US will subject that person to a possible revocation of their status as a permanent resident. For some people whose spouses have to remain in their country of origin for a reason perhaps related to taking care of elderly parents, that individual could not meet the resident’s time requirements in the US and simply doesn’t want to spend the money to become a permanent resident knowing that is going to be taking away from them.
Other people have small children that they don’t want to come to the US right away and the spouse is taking care of the children. They may want to wait until the children have finished a certain amount of school in their home country.
Any one of these is a reasonable and often common explanation for why a spouse might not become a permanent resident. There is no requirement in US law that both spouses in a marriage become permanent residents. It is entirely possible to file one case for the primary applicant and then at a later date file a follow to join case so that the spouse can eventually come to the US at a later date.