If you look at the service that want access to all your gmail data - many promise something "free" but then mine that data (in the fine print) to send you offers, alert you to "savings" etc.
I automatically turn down apps that say they need access to my entire google drive and all email. Why not just ask for permissions for a single app specific folder? Ie, fax apps -> they should just store inbound faxes into one folder rather than asking for full drive access.