Why declare the function as async when the other function inside the function block is itself an asynchronous function

const fs = require('fs').promises

const filePath = './me.txt';
async function  readFileAsync(){
 try{
    const data=  await fs.readFile(filePath,'utf-8')
    console.log(data)
 }
 catch(err){
    console.log(err)
 }

}
readFileAsync()

taking the above code as an example.We know fs.readFile() is an async function and returns a promise and await will return the resolved value of the promise.Then why do we need to declare the readFileAsync with the async keyword?