Well just because you have no evidence that they're doing something, doesn't mean that they're not doing something. And just because I have no evidence that they're not doing something, doesn't mean that they are doing something.
The difference is, that I just said that "I'd like to think they have at least done something", but you're stating that they are "not doing anything" as if it is a fact, something you have evidence of and know for certain.
As for the Youtube channel you linked to... why didn't you just send three copyright strikes? I'm assuming it;s because you're only allowed to send one? Then Envato would only be allowed to send one as well... you'd still need somebody else to do it. How do you know Envato haven't already sent a copyright notice? Have you reported the page to Envato?
I'm no expert on what actions a company can take in these instances, but I would have thought that the copyright owner would always have more options, than somebody who doesn't... no matter whether they are a company or not.
As for reversals, you're probably right... less pirate sites would result in less reversals, but there will still be instances of stolen credit cards and the like where it's the person who had their crd stolen who is the one that initiates the reversal.