If you are going to use the music to entertain your customers, pay for it like you're supposed to.
Buying music (I assume that is what you meant), will not let streamers use it, thus there is no meaningful solution as of yet.
Legally using copyrighted music is not exactly an impossible task. I mean, it's basically the entire business of some radio stations, and some stations are quite small.
Now, is it worth the effort and cost for a Twitch stream? It depends on how much value the music brings. There's also CC or royalty-free music, if a streamer just wants some music playing.
If you want music but you don't want to purchase rights, there is plenty of creative commons licensed music available.