It's because secular music glorifies worldly things and actions that are sin. When you listen to them you'll be thinking about the sin or even committing it ( by thinking about someone lustfuly for example). You'll be feeding your felsh and changing your mind set slowly(dont listen to that just a little excuse in the back of your head you will get carried away) and that my friend will tear u apart from God the same goes for most secular movies n series. God bless you 😊❤