It seems like I repeat myself and probably I do yes, but just think about it.
You see more and more bands doing this because making music cost money (buy or maintain their instruments, hire a studio, record their music ideas), touring around the world to entertain you (and ofcourse themselves) well then you need a bus or car, gas, food, a sleeping place and ofcourse the planeticket if your touring country isn't near your country.
That's why I put concerts on here too of so many bands as possible that I like and on my twitter too. That's also why I show songs of bands that I saw live on YouTube. Because I want to make them more known around the world, since they are good bands and nice people that deserve to have their dream(s) realized.
So the bands/artist/musicians gain nothing if you stream it for free or if you download illegally. Spotify or Deezer or something like that is already a big improvement since you pay a little for that (mostly) and you can get to know a lot new bands that you never even heard of (for a very low price).
But the best way to make sure your bands keep on making music is:
buying the albums, t-shirts and other merchandise on bandcamp or iTunes (and similar sites where you can buy albums), the stores of the bands themselves online and at shows/concerts.
So I think I said enough times for a while that (making) music isn't for free, but think about it and you'll come to the conclusion that you are partially responsible if you expect new music and more shows of the bands and artists you want to see!