It is used for better readability of enum statements

Below is a switch statement paired with an enum

enum Phone: String {
    case iphone11pro
    case iphonese
    case pixel
    case nokia
}

func getSeansOpinion(on phone: Phone) {
    switch phone {
    case .iphone11pro:
        print("Great overall phone")
    case .iphonese:
        print("its alrigth, but a small phone")
    case .pixel:
        print("great camera")
    case .nokia:
        print("great durability")
    }
}

getSeansOpinion(on: .iphone11pro)

output

"Great overall phone"

If you are using switch statement without enum you have to have a default statement

let matchmakingRank = 23

func determinePlayerLeague(from rank: Int) {
    switch rank {
    case 0:
        print("Play the game to determine your league")
    case 1..<50:
        print("You are in BRONZE League")
    case 50..<100:
        print("You are in SILVER League")
    case 100..<200:
        print("You are in GOLD League")
    default:
        print("You are in a League of your own. We don't know where you are")
    }
}

determinePlayerLeague(from: matchmakingRank)

output:

You are in BRONZE League