Because I agreed to give it to them, for one.

For another, I know what Google is. And where it is - they have an address. They're in the US. I could, if I wanted, sue them.

Compare that to a literally limitless number of unknown organisations all across the world? Yeah, I'd say Google is better.

Because at least then you know who has your data. If I agree to Google having some of my data because I trust them with it to some extent that does not mean I want to give any third party access to that data. And I'm not saying there's any reason to trust Google with your data, but at least you'll know who really has access to that data.