I think you missed the issue with the Dropbox comment. Look back at it. He talks about using Linux, FTP, curlftps, SVN, and doing a network mount.
The comment isn't actually even talking about providing the same service, so they mention emailing themselves files and usb drives.
The problem was there was a big technical hurdle to locally network mount a file system. Especially across OSes. It's even harder to do it non locally. Sure, it's not hard if you're familiar with that stuff. Sure, it's not hard to learn if you're comfortable in the terminal. Sure, today you can use rclone. BUT that's not a tool my grandma can use.
On the other hand, we're not talking about tools my grandma can use. We're talking about tools a programmer can use.