Its for marketing. Either you invite 30k ppl, or you invite 2k ppl, but some of them with thousands of viewers to market your game. They won’t listen to them, because again, the drawback is far to big.
Just because no other company has done this (even tho thats a bold statement without proof), doesn’t mean blizzard will pay attention to every Streamers request and do it.
Its simply not worth it, Blizzard knows classic has to succeed or its the end of Wow, becaue classic failing will be the end of it. Everyone hates Bfa, theres less and less people on it everyday. Alot of ppl has no faith in the next expansion. Classic is the one redeeming factor for Blizzard. Also, the ones working for classic are so passionate. Just look at Omar, the god that made this work, took the game home for a week and came back with classic working with the BFA launcher.
The team they have is very passionate for the game to be as it was in 1.12 as it possibly can. Their communication is 100x better than it has been for the past 15 years.