The other replies are missing what analytics is really comparable to. With a standard purchase, we have an exchange of the minimum necessary information at the point of engaging in a mutual financial transaction. The bookkeeper can examine that transaction after. They can look for patterns in what receipts have. That's fine.
Analytics isn't that. Analytics is tracking a customer walking into the store and looking for which store they came from. Analytics is noting down how long a customer spent holding a blue item, if they looked at a big red item, and noting it down because it might matter. Analytics is seeing how the customer went back and forth between one aisle and another. Whether looking at one item made them less inclined to look at the next. Analytics is hoarding all of that information and keeping it even if the customer doesn't make a purchase.
Of course stores have been looking at how and why and when customers shop for years, but through consensual studies. They learnt to put the fruit at the entrance and the sweets at the exit. They learnt to put their high value items at eye level. And they didn't do it through spying and analysing the behaviours of everyone walking through their doors. They didn't keep years of CCTV with the sole excuse that they might want to see how long you lingered between deciding on diaper brands.
The web has no excuse.