The reason for masks always has been to flatten the curve. The hospitals are too full for everyone just to get it and get it over with, so people without COVID can't get medical help. Right now, the CDC recommends everyone older than 2 years old should wear a mask indoors. This is not just to protect kids but prevent them spreading it.
Source: https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-si....