>>s1k3s+Z5
It logs requests to the site, which is far less invasive than the fine detail of browser fingerprinting and tracking that JS allows: JS can see your mouse pointer's position, how long you spent on each area of the page, which parts of the text you selected, and many
many other things.
Things like this are seriously creepy: https://www.crazyegg.com/blog/mouse-recorder/