To answer your first question, we make a point of taking down games that people upload to Itch.io without permission, but policing the rest of the Internet is simply not feasible. You must talk to the people in charge of wherever a pirate copy of your game was uploaded.
The other issues you raise being more subjective, I won't say much. Just that Steam DRM was cracked long ago, while Itch never had any, yet plenty of creators sell their games just fine. People pay when they want to support you, not when they're forced to. In fact, force them and they'll quickly decide they don't really need to play your game. Would you rather have your game played by pirates, or nobody at all?