I think Weather Forecast apps are popular because people like knowing they need a rain coat, or not by reading the weather forecast on their phone, tablet, or computer.
You need to know the weather 24/7. I know when I go to school I need to know to either leave for it early or get out of there early if bad weather is coming.
I still mostly use the radio, or TV news since they seem the most convenient for me for staying updated on weather since I listen to the radio, and watch TV news on most days.