Jammming Step 87 .map syntax

Hey we are using the following expression:

.then(jsonResponse => {
            if (!jsonResponse.tracks) {
                return [];
            }
            return jsonResponse.tracks.items.map(track => (
                {
                    id: track.id,
                    name: track.name,
                    artists: track.artists[0],
                    album: track.album.name,
                    uri: track.uri
                }
            ))

Why are we using .map(track => (…)) and not .map(track => {…}) as usually with arrow functions?

the () parenthesis replace a return statement!