I can't speak for other forms of credentials, but I have found AWS to be *embarrassingly* pro-active in finding plaintext AWS credentials in public repos, usually within minutes, and immediately disabling them - then telling us about it.
Some have said "ooh they should tell people first" - but I strongly disagree! "If AWS finds this token in the wild they WILL shut it off and you will have an outage and it's your own fault" is a delightful way to get engineers for whom best practice is not a priority to sit up and take notice. Being able to point at the 800-lb gorilla makes my job easier. A big, inevitable but easily avoided failure mode you can point out is one that can be used as a forcing function. Other providers should follow suit.