In mainstream Usenet such files are very common. If your client handle them properly you should get an mkv video file at the end (no password required). If you have a bunch of strangely named files, then you client can't handle obfuscated downloads.
If you never saw them then you probably download very specific content where posters don't care about DMCA shutdowns and post in plain names. Or you download password protected files shared on forums. In any case, if you don't care about obfuscated nzbs, then you represent a minority of Usenet users
What I'm trying to tell here is two things:
- unpacking of obfuscated posts on the fly is a difficult thing;
- there are a lot of other more important things for a "powerful" downloader.