You obviously don't understand what plagiarism is and have the myopic view that Steem is only for long form content.

Those posts are all attributed and sharing/embedding them is encouraged by the owners. It's literally doing what the creator hopes for. The plagiarism angle is moronic.

What you actually have a problem with is short form or unoriginal content. Social networks are largely about sharing links and opinions. Steem needs to grow so people are buying it and keeping the price up and so there are people to upvote the posts. Mainstream growth is short form and link sharing.

Rewarding short form content as well as long form is better for Steem. Most of the internet are not long form authors, why would someone who's not a long form author going to sign up and vote and buy Steem if they are going to get slapped down for trying to use it like it was intended. You do know the name Steemit stems from Reddit right? A place where link sharing get's upvotes as well as long form content.

Sites like DMania and Zappl understand that not everyone is a long form author and Steem is not exclusively for them.