Macbook Pro Screen Scratches

So, my Macbook pro which I bought in 2014 started to get some scratches on the sides of the screen for unknown reasons. I find it weird how all these scratches kept on coming out without me doing anything different to my screen as I did with my previous laptops. My Macbook is well looked after and it's even protected by a Thule body cover. Can someone tell me how these scratches just randomly start to appear on my Macbook? A photo of my screen is attached below: