Spotify doesn't fall into this category because it isn't considered Internet radio. Spotify is a streaming service that pays a majority of its ad and subscription revenues to rights holders (i.e. labels and publishers).
To add a little clarity, the reason that Pandora wants to lower their royalty rate is because they are currently running on, what seems to be, an unsustainable business model for the future. Their royalty rates are too high and they're paying out too much of their revenues to keep up their operations in the long-run. They also feel like they deserve a fairer royalty rate based on the fact that terrestrial radio (traditional AM/FM radio) in the United States does not pay royalties to the artists that perform the broadcasted songs, and only pays the writer(s) of the compositions via performing rights organizations (e.g. ASCAP, BMI, SESAC). Because Internet radio services like Pandora think this is unfair to hold a double standard for both terrestrial and Internet radio, they are trying to fight to pay less so that their businesses can be sustainable in the future.
Also, it is easy to assume that the royalties paid out by Internet radio services like Pandora are negligible. However, this is not the case. Even artists on the rise like French Montana are projected to make over $100k in the next 12 months from Pandora alone. More popular artists like Lil Wayne make up to $3 million/year from Pandora (source
). Essentially, artists can make a significant amount of money from Internet radio, which is especially important for those artists that do not write their own songs and thus, do not collect on terrestrial radio performance royalties.