Because 90% of all music enjoyed by most people is under copyright and searching for music not under copyright that you can listen to and genuinely enjoy is not anybody's idea of a good time.

Nobody wants to worry about this stuff.

As long as the purpose of the stream is not just streaming music i don't see the problem however I'm certain the MPAA and RIAA would not agree.

Why don't people just play the music they want in the background when watching these videos?

Probably because it's a lot more fun to have an interactive player where people can vote what to play.

Beside if you always play the usual 200 songs you listen to when are you going to find new songs to listen to.

Listening to music is a group activity a lot of the times and you find new songs by doing it.

There's only 3 ways to find new songs and 2 of them suck

1. Listening to top hits in hopes that a few match your taste

2. Using recommendation algorithms on Spotify and other streaming sites

3. And the on that give you the best results hanging out with like minded people in real life or on the internet and seeing what their listening to.

Bear in mind, copyrighted music doesn't just mean "Stuff from the top 40s". Music that's in the soundtrack of a game is under copyright.

So the answer to the question "Why do you have to use copyrighted background music for streaming of a game" is "Because playing a game with the volume at zero kind of sucks".

edit: And obviously that's not the entirety of the concern; there are definitely some streamers who play essentially radio music (or anime music or whatever) over the soundtrack on broadcast. I agree that stuff like that doesn't necessarily need to happen. But using a broad brush to say "No broadcasting copyright music on twitchtube" is both not a good idea, and exactly what people are worried will happen.

Because part of listening to music is that I listen to music which I like, which means Rise Against, the Red Hot Chili Peppers, et al.

To be honest, you're living on borrowed time. The only reason twitch would allow this is because it has flown under the radar so far. It's not a reasonable expectation that you can forever have a service that will let you stream copyrighted material to people.

If they are good or not, the laws exist. Once Twich is under Google's umbrella, they will be pressure by the content owners to enforce those copyrights. Maybe that's not happening today because Twich's community is smallish (compared to Youtube) but once they are "integrated" into the copyright notification/enforcement framework, end of story.

what kind of a question is that? Are you a human being?

maybe a restatement of the question would help

why do you expect to be able to broadcast copyrighted music for your own enrichment without paying the copyright holder?