When I worked at Google, almost all developer workstations were running Linux. That alone really should be plenty of justification for having such a client. They did not.
I'm not saying this is the right move, but I'm explaining why this project hasn't been funded.
At my current workplace I use a FUSE driver to get Google Drive in my file browser and I wouldn’t have it any other way.
There is FileStream or whatever it’s called, but it’s never coming to Linux so who cares.