This is an incredibly niche feature today because no releases come packaged in archives. Furthermore, to my knowledge you can't really "stream" archives.
I'd say the majority still are split into rars for the initial scene release but by the time it comes to the public trackers, and even many private trackers, someone has already unrared it for you.
They still do come packaged directly from scene releases. Smaller private torrent trackers have these releases. Public trackers usually contain just the media files so people don't have to unzip. But I agree, playing from archives would be a great feature.
