The more difficult it is to strip DRM, the fewer pirate captains there are. You don't need to take out every pirate to end piracy; you just need to take out every captain.
So if only Paisleybeard and VikingVik can crack the GoT DRM, you maybe only need to get cooperation from the Croatian and Swedish police for a few weeks, and then you get some amount of time when pirated shows are no longer available. But then Swashbuggerer and NotSoJollyRoger and Plaidbeard step up, and the pirate crews flock to their standards. But for a time, some people who might have otherwise pirated may have paid. But then you're back to talking to the American and Filipino and Scottish police. And if one of your captains is in a non-extradition country, you may have to talk to Pinkertons or ex-military contractors.
If it is trivial to crack the DRM, everyone can be a pirate captain if necessary, with a crew of only themselves. You will never, ever stop piracy for longer than a few minutes in any pirate-friendly household with that kind of DRM. That's like the difference between posting your property and putting up an actual fence or wall. It is just a virtual boundary that has legal consequences in the out-of-band enforcement system.
And don't forget that when pirate captains voluntarily retire, or are forcibly retired, they can still publish "how to be a pirate captain" guides for the media-seas they once sailed. They can distribute models for 3D-printing your very own pirate ship. So the DRM-makers have to put constant effort into changing tactics and updating technical countermeasures to fight that kind of fight. It gets to be expensive, because the defense has to be perfect, while the offense can breach it through any ant-sized hole. Furthermore, the analog hole will always be there, and every paying customer has the keys to your fortress gate.
