Perhaps it would be better if they saved and invested instead
If you consider yourself as, say, a Mexican 30-year-old who comes to the US and works as a carpenter, would you prefer to save your earnings and invest them (despite having little formal education, and thus being unlikely to invest well) while your wife, son, and parents continue living in a shack in Chiapas? Knowing that they would despise you for hoarding your earnings while they scraped by? I bet you would send them part of your paycheck. The opportunity cost of saving that money is too high.
If you consider yourself as, say, a Mexican 30-year-old who comes to the US and works as a carpenter, would you prefer to save your earnings and invest them (despite having little formal education, and thus being unlikely to invest well) while your wife, son, and parents continue living in a shack in Chiapas? Knowing that they would despise you for hoarding your earnings while they scraped by? I bet you would send them part of your paycheck. The opportunity cost of saving that money is too high.