A virus scan doesn't always detect viruses.
This rule is implemented to prevent people from sharing viruses, keyloggers, etc.
Even an outside download link that provides a legit hack could be dangerous, as it could include an auto-updater that would then download malicious content to the user's PC.
Uploading it on MPGH with the approval system we have going on now ensures that files are thoroughly checked before regular users are able to download them.
Long story short : The safety of our members is key.