It's all about site traffic. These sites have this content to increase user traffic and popularity.
This is a major motivator for the guys who take the time to scan their games for their sites. Why shouldn't they be upset when somebody shortcuts and takes their work?
Now, it may not be legally actionable when VGRebirth takes their scans without permission, but I think it's entirely appropriate for them to be called out when it's blatant and obvious.
BTW, I found the name "Optigrab" to be hilarious. I'm rather shocked they didn't just hotlink the images to save bandwidth.