There are many reasons for this.
This is an ad supported initiative. We need money to keep the site running and to pay for the internet costs which run into hundreds of dollars per month alone and to source the material that we use. The site does not bring much money but it goes a long way in defraying these costs.
Proof that our strategy is sound is that we used to have many rivals that have since gone under because they could not handle the cost. We need to make sure we carefully balance students needs with ours too.
Once we allow people to download these notes they will quickly proliferate and start photocopying them. People will not visit the site as often as they should and we will die just like our rivals. There are students who will need this site next year what will they do?
Those who want to download these notes because they do not have access to reliable internet should just use traditional methods of studying just like they have always done. I went to school not so long ago and we had no internet. Yes I got 15 points without Google!
Allowing people to download papers violates ZIMSEC’s copyrights; possibly according to our reading of their copyrights. If you want the papers ZIMSEC sells them at $2 a copy. Think of our site as something like YouTube, Spotify, Hulu and Netflix. You can view or listen as much as you want but you cannot download the song. We are going to be creating a Spotify like app that allows you to save the files for offline use but does not allow you to keep them indefinitely as you seem to want to do.
The content is always changing so allowing people to keep a single hard copy is like letting them have a physical copy of an antivirus. It is bound to get out of date soon.
I could go on but I think you get the picture.
Hope you found this useful