heh true, they might not care at all - Apple makes more $$ in a quarter than several Spotify market caps. But, here's a few theories: if Spotify keeps calling itself the "leader" in streaming and Apple decides it wants this to stop, it would be an easy/cheap way to impact Spotify's brand negatively, and even potentially bring them down entirely. Alternatively, by driving the price down, it could also force Spotify to explore selling itself at a low price (see: Pandora), and if Apple wanted some fast/easy subscribers, it could acquire them cheaply.