unwanted iPhone cookies reappearing

iPhone: after I delete all unwanted cookies, they come back, even when Safari is not used and the iPhone is turned off. I get cookies from sites that I have never used (e.g. Facebook, Twitter). I don't use Google nor Amazon, but they put in multiple cookies anyway. Many advertising cookies come back. I can delete all cookies, set iPhone aside and not use it; come back after a while and all the cookies are back.

Safari (across devices) allows cookies to be installed, including from sites not visited, and when Safari is not used / off. MacOS has an app "Cookies" that works very well, but the iPhone does not.

Apple seems to remember my cookies and put them all back, from all sources.

How can I stop this?

Thank you.