Possibly if you use an ad-blocker (or maybe if you don't) you've encountered this irritating popup:
It covers part of your screen until you click it. Your reasonable reaction might be, "Every website leaves a cookie -- what's the big deal?" But if you click "give me more info" you find the real reason -- it's the third party tracking cookies they want to put on your device (see boilerplate below from the VoxEU privacy policy). Why not say this on the website, as long as they are going to the trouble of interrupting the reader's "user experience"? This is a minor, sleazily disingenuous form of Dark Pattern: coercion disguised as choice.
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