Again, there is no such thing as "illegal by default". Do you think nobody has a copyright on the Linux kernel? A lot of people do. The same applies to virtually any free software. There is also software which is free (as in beer) but not open-source, yet the authors still have the copyrights.

There is *a lot* of free (as in beer) music available all over the internet. The artists nonetheless have the copyrights on those unless they explicitely dedicate their work to the public domain.

It is *not* possible to know beforehand whether something you download is given away for free or whether someone is uploading it without permission. I have no idea why people would voluntary dumb this down to "it is illegal to download copyrighted material" unless they have some interest that people believe in this view. There has been *a lot* of lobbying and brain-washing since Napster. Many things that were perfectly legal in 2000 are either illegal now or have been pushed into a grey area where it depends on the exact case.

Maybe it's just that people have a hard time if they cannot stick to simple rules or they just cannot believe that there isn't a (simple) solution for everything. If there was, for example, spam wouldn't exist anymore. Of course, you can simply declare all file transfers illegal. There's your simple solution.