Scanlines are more of a TV thing when displaying low-res content, I don't remember the technical explanation exactly but it had to do with filling out low-res 240p content on the screen. As far as I remember, PC CRTs didn't display scanlines, they work differently from TVs. Hyllian and most well known shaders are based on TVs. There are some shaders that change the way scanlines work past a certain resolution, others display them all the time.Hyllian. Why no scanlines?
I may tune them down a little for higher res games.