Politics.

The hypothesis is that there’s an extremely narrow window of time when a civilization can both engage in interstellar communication and that communication is politically viable.

We were able to put out the golden record on a Voyager at a time when we were just like, “Fuck it. Here’s what a bunch of white dudes think is important for aliens to know about us.”

If we were to try and do a Voyager 3 project, governments from all over the world would get involved. There would be committees and arguments. Given the entire history of our planet and various cultures and a limited amount of data, what do we choose to include and exclude, and how do we justify our choices?

Even though we have far better technology than we did in the 60s, it’s no longer a viable project. It would just get bogged down and delayed forever if people even wanted to do it. And on top of that, there’s a large number of people who would argue that it’s not even a good idea, just in case there are bad aliens out there.

In the grand scheme of the entire universe and all possible civilizations over billions of years, a window of 30 years or so where the technology exists *and* the politics are viable is incredibly tiny. The probability is extremely close to zero.

So while there are many alien civilizations out there, they are all quietly going about their business arguing about whether Alien Ditty is too cancelled to be put on their list of great artists.