Highlight What?

I don’t understand what people highlight sometimes. You get a range of people who use the highlighter for different reasons. Some people normally have one highlighter: the basic neon yellow. Then you have the highlighter fanatics, carrying their different highlighters of different colors and sizes. I can understand two colors, but five is pretty unbelievable. Is hot magenta really necessary? But most of the time, it’s not how many highlighters that people have that irks me. It’s what people highlight. Sometimes you highlight an interesting phrase or important keyword. But if it’s in bold, why do you need to highlight it? Show some restraint! The highlighter is to highlight. What’s the point of highlighting the entire book? Is it to show that everything is important? Or is it because highlighting makes it look pretty? Either way, it annoys me.