Why are the extras left out in the uploads?

I’m sure there are people who would be asking this question at the back of their head.
So I see a lot of video uploads of movies and TV series. Some includes the featurettes seen on the DVDs and/or Bluray such as interviews, behind the scenes, even the inclusive pdf scripts. But most of the uploads only contains the movies or the episode themselves.
Reversing the question, why do some uploads have extras?
Answer #1
Because some people like collecting full DVDs or Blu-rays..
Or they want to sell them on the black market
Answer #2
I would pass on any post that had extars included in the rar files.. waste of download time.
Extras are a waste of space on a dvd/bluray – they are only there because they can’t think of anything else to put in the excess space of the disc.
I can’t stand extras, i have no interest in listening to some self-important waanker banging on about why he put this sound here or that colour there.
The ONLY extras worth having are the bloopers, and I don’t mean this crap the yanks put in where they deliberately bugger-up lines and make slap-stick stupid faces, I mean REAL extras where they genuinely stuff things up.. (seems only the Poms do bloopers properly! Smeg Ups Rule!)
Answer #3
Nel replied: Because some people like collecting full DVDs or Blu-rays..
Or they want to sell them on the black market
Thanks. It’s likely for those people who download than upload.