If you use #GoogleDrive, you are also allowing Google to do whatever they want with your files: they can read them, copy them, give them to anyone else, make derivative works, even publish them online without your permission (see attached screenshot). #DropBox is similar.
In other words, private files uploaded to Google Drive are no longer private.
You might want to try #privacy aware #NextCloud instead, which actually lets you control who gets to see/use your stuff:
https://switching.social/ethical-alternatives-to-dropbox-google-drive-and-google-docs/
Note that the second sentence narrows what they can do with your data to basically just running and improving the service. You.'re not letting them (e.g.) sell the data to third parties.
(Which is no to say they can be trusted; stick to computers you control as much as possible, especially for valuable data.)
It lets them share your data for the sake of "improving services" and "promoting services" and "developing new services", which could mean absolutely anything.
It's so vague that it is a blank cheque for Google.
Google Drive's terms specifically mention Google sharing your private data publicly for the purpose of creating new services.
...which is what they did when they launched Google Buzz. Gmail users' private contact lists were displayed publicly:
https://www.pcworld.com/article/189081/go
There was an opt-out option, but you could only opt out after your contacts were already revealed to the public.
This isn't a theoretical problem, Google have past form on not respecting privacy.
@switchingsocial @suetanvil I'm not sure a judge would think that means absolutely anything. If Google just started displaying everyone's private content publicly, it's hard to argue that it's for improving the service.
Legal documents have a tradition of how they are interpreted, so while it may sound vague to you, lawyers and judges tend to already have an understanding of the intent of the wording and don't generally interpret the language in a way that's most harmful to one party.