And Google uses some badly tuned and not understandable by humans, and also constantly changing, machine learning algorithm to decide to serve you or not.
When something goes wrong with this, you have a a fairly small chance that you can reach a human to override, but it will be an overworked underpaid contractor
somewhere and your chances will be poor.
If you talk long term (decades), it is quite possible that Google falls out of favor and becomes legacy, like Myspace, with not making that much money anymore. We all know what happened to the Myspace data, they just deleted most of it at some point.
Essentially it's a lottery with your data.
Now a badly maintained hard disk is a data lottery too, but it's not clear to me the chances to retain are that much worse than Google's.
I think it's foolish to shoot down advantages in practicality and fluency of use on the basis of a decades long event for the vast vast majority of use cases. My company hasn't been around for decades and we don't use any particular spreadsheet outside of a select few for more than a couple months at a time. You'd lose all credibility arguing against G-suite on the basis of losing your data/getting your enterprise google account banned, because it would cost the business so much time and confusion relative to the ease of cloud solution.
I've already had disks fail, never had an issue with Google Docs being down, and if it happens I think it will have been worth it.
You trust your hard drive to never fail during crunch time, or Jane Doe in accounting to not lose the flash drive that gets shared around the office every quarter?
I'd take "generally highly available" vs "trusting my local copy" almost all the time. And as for using something like a Git'd Excel document: most people won't do that, and Github can go down, too.
Just because Google Drive isn't perfect, doesn't mean it's not better/easier/more user friendly than what has been the standard for years.
Easy to share
No need to backup
Cross platform (works on Linux)