Its important because lets say for example decision-making in business. It is important because there are consequences to making the wrong decision. When managers are making decisions on behalf of the company, it is important that they weigh their options because poor choices can result in legal, financial or brand issues.
Being underweight can contribute to a very frail and weakened immune system. It can make one feel tired mentally. And can also affect the bones by making them very brittle and frail sometimes.