Some providers (namely ISPs) simply dropped the binary groups and kept the text ones. So piracy alone is clearly not what killed it. In fact, Usenet really only exists today for piracy, so if anything, piracy actually saved Usenet. Just for a different use case than originally intended.
I mentioned this in my comment. As a technical matter, you could simply not take binaries. But as a commercial matter, you could not; if you didn't have binary groups, you weren't offering real Usenet (and if your binary feeds weren't ultra-reliable, you were offering shitty Usenet). The result was a consolidation of the platform down to a small number of providers willing to invest large amounts of resources to placate binaries users.
If lots of people aren't running NNTP servers, there's not much reason to use Usenet. By the time Reddit and Digg rolled in, it was no contest.
> But as a commercial matter, you could not; if you didn't have binary groups, you weren't offering real Usenet (and if your binary feeds weren't ultra-reliable, you were offering shitty Usenet).
None of the ISPs I had from the mid '90s through 2010 ever had reliable binary news feeds. Most would be missing too many articles, or articles would expire within hours and the download could never be reassembled.
Anyone who really wanted binaries started using paid services and just use their ISPs usenet feed for text discussion.
This is exactly my point. It's why Usenet consolidated and then died: because smaller firms lost the ability to provide the whole service, which was overwhelmingly abused as a file sharing network.
