They have to set up the replacement (topics API) before they get rid of the previous solution (third-party cookies). Sites need time to adjust and implement the

They have to set up the replacement (topics API) before they get rid of the previous solution (third-party cookies). Sites need time to adjust and implement the new systems. They also need to not make sweeping changes to the ad industry that could be described as anti-competitive or monopolistic. I doubt they'd get away with just turning off third-party cookies in their browser.