why not ?
give us hardcore server with new rules
No flying mounts
No LFG/LFR
No normal raids you can only go heroic raids
much more punishing Environment in order to force us into playing with other players stronger mobs make it so we can solo maximum 2 normal mobs 4 mobs would overwhelm us
make elite mobs much stronger so we can kill them only with group
make heroics dungeon twice as hard on that server
no guild leveling
look at path of the exile everyone loves the hardcore servers and people complain ALL the time about this LFR /fly mounts and want them removed so lets make 1 server call it hardcore or whatever and lets see how its go i can promise it will get flooded with people and blizzard will be forced to make more hardcore servers
while many dislike it just as many would LOVE it many old players would come back for it Kripparrian /kungen for sure would come back to play it and so many more players would resubscribe !
i cant think of one single reason not to do it.