Blizzard does nothing about it because its "hard to prove". Ive recorded videos, sent them in.
Blizzard relies on what they can prove, not what players claim. Even if you're honest, how can they tell by video that someone didn't fake this by re-editing or using a demo or illegal server to frame someone?
People dont magically go from perfect connection to terrible connection right when theyre near death or in a troubling situation that will cause a loss.
You sure about that? I know on my old computer, lag would go through the roof if I were in a particularly thick PvP battle or raid fight. Hell, it was a while before I could even stand to enter Dalaran.
Theres people on my server who blatantly hack, and use latency hacking as well, brag about it too. They been doing it since Burning Crusade, received multiple reports against them, and still nothing has been done.
Why do you trust them that nothing has been done? They have everything to gain by lying to you, and as has already been stated, this isn't the simplest thing in the world to prove.
Apparently their money is better than mine since Blizzard allows things like this to continuously go on.
Apparently, you'd have Blizzard take you at your word when it comes to banning people, and your desire for this to come to an end makes the solution manifest instantly, cheaply, and with no false positives.