iCloud "this type of file must be compressed" to upload

I currently have the Carbonite (desktop backup) app on my phone. To view an (MS) Excel, Word or PDF file, I locate the file and click to open on the phone. If I wish to edit the file I send it to (previously, the beta Numbers or Pages) the now free MS Word or Excel app.

I thought I'd give the iCloud a try. I created a new folder "Word & Excel" and then I dragged my desktop Excel and Word data folder tree to the new cloud folder. The website said that 34 files could not be uploaded saying they had to be compressed. Since there was no further information, I can only assume that that means the files are too large.

If this is true, it's really strange since none of my data files are that large relative to the allowed total storage of the iCloud or even a run of the mill Word or Excel file.

So I'm going back to what I've been using as stated above but I am curious why Apple has this seemingly dumb restriction?

Mark