For example, Search could be expressed as a separate permission and API operation. I see no reason why you need full file access to do a text search - the OS API can, and should, handle that.
The trouble here is people store all kinds of things in Google Drive, includes photographs. These could easily be exfiltrated to a server. This could cause identity theft, black mail, you name it. Performing a text search IMO is not a good enough justification for the potential risk of that situation.