It’s hard to say what deals the major labels get (they won’t tell), but I don’t see a huge benefit beyond piracy besides giving people a legal way to freely listen to your music. Digital music news says:
If Spotify, Rhapsody, or other streaming services won’t answer the question, maybe indie labels and artists will. These figures are from an independent catalog of 87 albums and 1,280 songs, as posted on The Trichordist. On Spotify, they seem consistent with reports of per-song payouts of roughly one-third to one-half of a penny
Either they see it as free marketing to out music on these services (probably) or they’re just really nice guys.