I'd prefer the direct zip, sure, but I'm just saying that it's not inconceivable.
If I'm 'downloading' or otherwise 'exporting' data from any service, I expect it to be all the data. Not a diff wrt the last time I clicked the button.
However, clicking "download backup now" is a very easy 1 click operation, and I can just store that zip file wherever I want. Done.
I mainly use Gmail via IMAP (and the web version when I need to set up filters). Therefore, I'm intrigued that folks seem to be interested in a 1-click-download kind of solution.