I guess integration with Google Drive is a big convenience for users.
But yes, if the cost of getting access is to high for indie developers, then it make sense to avoid Google Drive. Creating and maintaining your own cloud sync service for a specific app may not be worth it, they should investigate integration with existing Google Drive competitors/alternatives.
He gave a reason, and said he’s not going to answers why questions, so your guess is as good as anyone else’s.
We should be thankful that this person maintained the app and put up with Google’s bullshit for so long.
If you find this app helpful, consider supporting whoever is willing to take over maintaining the app or a fork.