That's actually part of the problem. The government should close down illegal establishments, and not just be blocking access to them.
The other part of the problem: Once the gov can tell the ISPs what to block (a) the block list must be secret and (b) the process can be very easily abused, with 'overblocking' being the standard excuse.
The same they would not block Telegram nation-wide just because some users are using it to upload movies to public gruops (yes, it happens) because most of the users just use it to talk to their friends.
I prefer to think of it as "conveniently shared". Here in Australia we have a problem with lack of convenience around legal avenues of digital entertainment, so there's not exactly an equivalent legal alternative to something as easy as downloading. It's a fragmented mess of services if you choose to play by the rules.
Regional restrictions, lock-in contracts, and free-to-air "rights" to particular programs exclusively means every platform plays a tug-of-war with viewers, trying to get their subscription dollar or eyeballs on advertising.
People will find the path of least resistance when the commercial interests around them close in with deals and promotions and hype we can't possible keep up with or remain in tune with. So we turn to the internet.
Not everyone is "illegal" all the time. I buy blu-rays of shows I really liked that I previously downloaded. Exposure to content otherwise never discovered has a value we are not seeing factored in to these arguments.
Unless, of cource, $activity isn't even illegal in that other country.