businesses and the government import them to support their sham service and debt based economy. the days of the export economy ended long ago, with over 60% of their gdp being services. with falling birthrates and an economy based on infinite growth and meaningless consumption you simply have to keep bringing them in to consume and work or everything comes crashing down. there are plenty of companies and schools being outright owned by foreign companies that sponsor those work and student visas, but it's the situation we have in the west. if the numbers stop going up there will be drastic upheaval, and every single person with power, influence, and money wants to avoid this at any cost.
United States