I recently tried to browse Groupon to see whether they had any interesting deals. After opening a couple of deals in new tabs, the site became completely unresp

I recently tried to browse Groupon to see whether they had any interesting deals. After opening a couple of deals in new tabs, the site became completely unresponsive and every page that I opened to ages to load. I noticed that uBlock was blocking hundreds of things and only after the counter stopped increasing, the page would become responsive. Solution was to open a browser that doesn't have an ad blocker and the site became pretty responsive. I understand that it's probably a bunch of tracking to predict what I want to see. But why would they need to much stuff if I'm probably there to buy stuff anyway?