The coronavirus pandemic is a situation with new information developing around the clock. Due to its serious nature it is important to seek out reliable sources of information.
Why might events be canceled or postponed because of COVID-19?
Healthcare is a limited resource. Each hospital has a limited number of doctors, nurses, beds and equipment for sick people. If we can slow the spread of disease we can help the healthcare system from becoming overloaded. This chart helps illustrate that concept of "flattening the curve":
You can read more here: https://www.nytimes.com/2020/03/11/science/coronavirus-curve-mitigation-infection.html