Some of those keys are public knowledge and only serves to tie what client it is (Chromium, Firefox, Safari probably) or otherwise stolen from one of those. This is a safe browsing API key, it's used to check if sites have been marked as phishing/scam/etc and is used to warn users that the site is known to be malicious. Others are used to tie analytics or ads to the app, so it goes into the right developer's account metrics.
I wouldn't call those leaked, they're meant to be embedded into apps and aren't considered as secret keys.
It's common practice to use API keys like that even if they're not so secret, just for the sake of tracking which app is making what requests and so people can't just openly use the API. You can easily shut down unapproved clients by just rolling out a new key, and it causes an annoying whack-a-mole game to constantly have to extract them from an APK.