Google has rolled out "Privacy Sandbox," a Chrome feature first announced back in 2019 that, among other things, exchanges third-party cookies—the most common form of tracking technology—for what the company is now calling "Topics." Topics is a response to pushback against Google’s proposed...
I read this article from top to bottom and didn’t find a clear explanation of why you should disable this feature.
It’s an underhanded way of implementing a browser supported foolproof adblock detector. Even its stated goal of “give advertisers a unified, browser backed, ‘private’ way of tracking you for advertising” isn’t especially appealing or useful when you get something better than that from adblock anyway. Turning it off will be reflected in telemetry sites gather about feature availability and hopefully low adoption numbers discourage them from taking advantage of this “feature”.
Because spying on you is bad. They mention the privacy implications in the article.