Siri refuses to answer certain questions about music unless you're an Apple Music subscriber
Another request made of Siri, to find out the top song in the U.S. in March 1983, produced the same result. An Apple Music subscriber asking the same question not only was given the answer, but also got to hear the song play. By the way, asking the question on Google Now produced a chart showing Billboard's top songs for March and April 1983.
Obviously, it seems that Apple is set on getting iOS users to subscribe to its streaming music service. Non-subscribers, at the very least, might have been sent to a link that could provide them with the answer. Instead, Siri has turned into a shill for Apple Music, and the result does not sound harmonious to iOS users.
source: TheVerge via CultofMac