At a company of any size, with compliance and complex sharing requirements, and advanced search and workflow needs, Drive is a non-starter.
Person A can only read document X because they are performing duty b on project y.
Not everything works with binary can/can't read scenarios.
How is this _not_ a binary can/can't read scenario? The person can either read it because they're performing the duty, or can't ready it because they're not.
I would suggest your security team do an audit with CloudLock (note, we acquired them at Cisco) and my guess is that it'll be illuminating / shocking.