Streamers almost exclusively use Java. There are certain popular games and mods that are only possible and/or easier to setup on JE. Achievement Hunter was one of the rare channels that used the console version at first and even them changed to the JE eventually. But they are not relevant anymore, weren’t for some time before their closure. Hyper massive servers, custom maps, automated gamerules with scripts, most of those things that make Minecraft creative and interesting to watch exist only on the JE.
Achievement Hunter is what made me wonder. I knew they used Java for Galacticraft but I thought they used Bedrock for pretty much everything else.
I also don’t know how popular streaming Bedrock multiplayer servers is. I think they are called Realms.