Why does the presence handler not work, although a similar message handler works? :\

func messageHandler(s *discordgo.Session, m *discordgo.MessageCreate) {
    log.Printf("Message!")
}

func presenceHandler(s *discordgo.Session, m *discordgo.PresenceUpdate) {
    log.Printf("Loggin!")
}

Why does the presence handler not work, although a similar message handler works? :\