It's to make it more difficult for scrapers. Google have been able to do all the tracking they've wanted for decades.

Think about it: if you want to set up something like jina.ai you need to build your own index or piggyback on Google. My guess is they use residential proxies to fire requests to Google then scrape the URLs.

Opaque URLs now give Google another gateway to detect circumvention of their anti-bot controls, helping them monetise their search index rather than allowing providers like jina.ai to succeed.