So-called "cookie banners" usually ask for your consent to much more than optional tracking cookies. By accepting you might be giving your permission to e.g. track you through various fingerprinting methods, build a profile and share it with advertising partners.

If they are aggressive enough to do fingerprinting, what makes you think they would abide to your choice? You do browser fingerprinting when you want to overcome people rejecting cookies.

An additional reason for not browsing the web without uBlock Origin on Firefox or other browsers with full support (not Chrome).