Access to SAP Notes

Why is access to SAP Notes, KBAs etc, restricted by S-User login? Is there anything so much secretive in there? It is just knowledge, right? Shouldn't atleast the PDF version be available to read without having to login? There are many other websites, which basically copies SAP notes and publish them on their website for free. They will all die down if SAP doesn't have this restriction, isn't it?

Or, is there such a functionality already available that I'm not aware of?

Thanks.