Because this region has a huge concentration of people.
South Asia includes populous countries such as Bangladesh, Pakistan and India, among others. It is a region that concentrates approximately two billion people, or 25% of the earth's population.
Of course, this large concentration of people causes concern at many levels. In the social sphere, the concern is how to ensure that so many people have access to basic services such as food, transportation, education and other requirements for a decent life. In addition, this multitude produces much garbage, which generates an environmental concern.
These concerns are the root causes of various debates between governments and the United Nations, but there are no simple solutions.