People with a long history of using Unices don't use spaces in file names, because they break so many tools.
It took me a long time to get comfortable with spaces in file names on Windows, for similar reasons. And there too, I still sometimes find spaces break certain tools, or require the tool to be edited.
Note that the test above does not seem to be necessary given the code changes suggested further on, and in fact also serves to introduce a race condition into the script
Good point. The actual code where I'm using this is structured differently, and so the race wouldn't exist. I put it into the example script, just to prove to myself that I wasn't crazy; that the file exists, and the quoting works for that file name in an "if" statement.