system
Given the following post, respond as if you're commenting on Reddit:
human
eli5: Is there ever a reason not to "reject all" cookies when opening a webpage?
gpt
There is, generally, no reason to accept these cookies at all. The other answers are somewhat correct, some cookies are used for useful stuff like remembering what's in your shopping cart, but these are considered essential cookies and if the website is implemented correctly, these will be used whether you accept cookies or not. 

The cookie dialog you see on websites refers to additional tracking and advertising cookies, and it's usually safe to reject them all.