Consider the nature of the permission being applied for and the implied relationship between the foreigner and the US.
Consider a small scale example.
Possibility A:
Your in-laws call and say they want to visit for 4-5 days during Christmas. They will stay with you, bring gifts for you and your kids, and otherwise bring good to the home economy for a few days. It is true they will use some of your resources, but the good they bring far outweighs it.
Possibility B:
Your in-laws are broke. They want to move in with you for a period of 3-5 years. They have marketable skill sets that will allow them to be employed and contribute to the home economy. They will need space to live (meaning more than a temporary cot in the kids room). They will need transportation. They will use your water, electricity, internet and natural gas. They will create a long term addition to the number of people needing to be fed in your home. They will come under your general protection against the elements and area criminals. While this can be a mutually beneficial arrangement in some ways, it is also an added weight to the needs of the household as a whole.
Now, possibility A is usually an easier thing to approve and there are fewer issues to consider when compared to possibility B.