Why are downloads limited to 200MB?

I see you are referring to the "Download All Uploads" feature on the submissions page. 

The 200MB limit is there to ensure that the user can download the files quickly. Trying to download all the uploads at once can take a long very long time, specially if the form has thousands of submissions, so the 200MB limit was set. If the user want's to download all the submission, they will need to download the files per set. So you can download the first set of 200MB files, then the next 200MB files, and so on.

You can check out this guide on how you can partially download each set of submissionsHow to Download the Submission Files. Regards.