Maybe it was just because I was little and new things were exciting, but I loved DVD extras. I remember getting Red Dwarf DVDs and discovering little bonuses and easter eggs hidden in the menus; though I think it was just a cool use of a new technology where the novelty has since worn off.
We still get DVDs from our library of whatever show we are watching now, even if we are subbed to whatever service it is on. No ads, deleted scenes, & bonus features? Sign me up! Even saves time, we can watch one episode in about 15 minutes less compared to streaming. Since we watch at night after the kid goes to bed those 15 minutes are more valuable than you’d think.
Additional material can be fun. I still laugh if you watch Galaxy Quest on DVD, and change the language from English to Thermian for all the dialogue.
Additional commentary, additional unreleased scenes, and behind the scenes are always welcome.
Sometimes additional scenes point to a different direction not taken, such as with Supernova.
Unfortunately some movies went to the well a little too often with their extended edition, special edition, ultimate edition, etc. I must have 4 different versions of Terminator 2, Blade Runner, and a film I didn't care for no matter what the version-- Alexander.
Sometimes the special editions are better. The Abyss for example. Zack Snyder's Justice League was a better version too.
Mad Max: Fury Road's Black & Chrome Edition was okay. Not sure it was needed.